LibKis Cla^k^ ^ t \ MOSQUITOES MOSQUITOES HOW THEY LIVE; HOW THEY CARRY DISEASE; HOW THEY ARE CLAS- SIFIED; HOW THEY MAY BE DESTROYED BY L. O. HOWARD, PH.D. DEPARTMENT OF AGRICULTURE, WASHINGTON, D. C. NEW YORK MCCLURE, PHILLIPS & CO 1 1) O 1 CorTRionr, .Tine, 1901. by McCLURE, PlIil.LII'S * CO. INTRODUCTION SOME years ago I was visiting- a family in the moun- tains. It was during a dry season, and water was scarce. There were no swamps, no lakes or pools, and the drinking-water was taken from springs ; yet mos- quitoes were so plentiful that it was necessary to screen the porches, that sitting out of an evening might be made possible. I asked where the water came from in which they washed their clothes, and they replied, as expected, " From a rain-water tank," which, as it happened, was sit- uated under the porch. I investigated the tank and found it literally alive with mosquito larvae. A i3int of kero- sene stopped the breeding, and as the water was drawn from a faucet near the bottom of the tank the kerosene did not injure it. The indifference of this family as to the source of their local mosquito pest, or rather their combined ignorance of and indifference to the subject of the breeding-places, was at that time — and it was not so very long ago — char- acteristic of people in general. It was my good fortune, through the wide-spread newspaper accounts of my kero- sene experiments in the Catskill Mountains in 1892, to become more or less identified with many practical experi- ments in the destruction of mosquitoes from that time on. Interest in the subject became very great, especially vi INTRODUCTION amon<:c summer residents of the country, and especially near the seashore, even before the a<;'t!ncy of mosciuitocs iu the spread of disease became established, and before it l)ecanie a .^tnierally accepted fact. With the very ^ler- fect proof that the mosquitoes of the g-enus Anopheles are instrumental in the carria^^e of malaria, the interest be- came intensified, and the late discovery of our Army Yellow-fever Commission in Cuba, that a mosquito is the conveyor of yellow fever, has added to the general interest in the subject. In fact, the whole mosquito question is a live topic of the day. Knowledge of mosquito lialuts is more general than at any i)revious time, and almost every- one is interested in the subject of mosquito extermina- tion. With the knowledge which we now ]iossess, it seems almost incredible that peojde should all these years have suffered, more or less patientlj^ the torment- ing- bites of Culex and the insidious but more dangerous ])unctures of Anopheles without making the slightest ef- fort to abate the nuisance and the danger, beyond slap- ping:, ill '1 reveng-eful way, at individual biters. In many places infested with mosquitoes nothing could be easier than to put a stop to the whole tormenting plag-ue. In many other cases the problem is a more difficult one, but in even the worst cases, by a judicious effort, which should be a community effort, and by the expenditure of a greater or smaller amount of money, much relief can be gained. In fact, Mr. W. J. Matheson, of New York, was quite right when, in th(^ summer of 1000, just before com- mencing a successful crusade against tlu' mosquitoes on the north shore of Long Island, he wrote me that there INTRODUCTION vii seemed to him to be no more reason for enduring the mosquito scourge than in allowing small-pox to ravage communities, as it used to do before the days of Jenner. Work against mosquitoes is being undertaken everywhere, by individuals and by communities. The interest in the subject, from both medical and lay points of view, has be- come so great that persons are not satisfied with half knowledge, but must know the whole mosquito story, and it has been with the purpose of supplying in some part this demand for information, that this book has been pre- pared. It tells what is known about mosquitoes from the biological point of view, from the medical point of view, and from the practical side. An especial effort has been made to show, in a straightforward way, to physicians how the different kinds of mosquitoes can be distinguished, and to indicate the characteristic habits and breeding- places of those forms which spread malaria and yellow fever. Directions are given for collecting mosquitoes and for rearing their early stages, and an especial effort has been made to display fully and practically the remedial measures which should be adopted in mosquito-ridden neighborhoods. TABLE OF CONTENTS PAGE Introduction, v CHAPTER I. Mosquitoes in General, 1 The Life Round of Mosquitoes, ..... 1 Parthenogenesis Among Mosquitoes, ... 4 How Long can the Larvfe Live Under Water? . . 5 How Long may the Larv* Live ? .... 6 How Long can the Larvje Live Out of Water? . . 7 Length of Life of Adult Mosquitoes, .... 9 Transformations of Mosquitoes Artificially Hastened, 12 Mosquito Songs, , .13 How Far do Mosquitoes Fly ? Are They Carried by Winds? 16 Carriage of Mosquitoes by Railway Trains and other Con- veyances, ......... 25 Queer Places in which Mosquitoes Breed, . . .28 Food of Adult Mosquitoes, ...... o4 Abundance of Mosquitoes, ...... 3!) The Northern Mosquitoes, ...... 42 The Poison of Mosquito Bites, ..... .44 CHAPTER IL Malaria and Mosquitoes, . . . . . . .48 TABLE OF CONTENTS CHAPTKR III. PAOE The Common MosciurroKs ok iiik (ip:\rs (Utlex, . . GO Dr. J. H. Smith's Ob.scrvations (HI (Uilc.r piiiigtns, . . 83 CHAPTER IV. The Malarial Mosquitoe.s ok tfik Gkxus Anopheles, . 91 The Ijifc History of J ;/'»y>//e/f^s- tudculipiujiis, . . 93 Eiir<)iH'an ()l)st'rvatiuiis on tlic S.iiMc Species, . . . 107 Natural Breeding Places of Aiiopliclcs, .... 109 The North .American Sp('ci«'s of Anopliclcs, . . . li:! Food of .\nopiieIes Larva', . . . . . .117 LenjJTth of Life of Adult Anoi)heles, 118 How Anopheles Bites, .119 CHAPTER V. Mo.'^QuiToEs AM) Yellow Feveh ; Mosquitoe.s and Fili- AHIASL'^ 121 The Yellow-fever Mosquito, ...... 131 Mosquitoes and Filariasis, ...... 140 CHAPTER VL OtHEII riENEHA OK NoHTH AmKRU^VN MOSQUITOES, . . 144 \u\ii \jnr\:i of Ali(>j>/i(fes itKKfili/ieiinis, . . . 100 1!(, 1!(A. lljill'-^Towii L;irv;i of .liiiij>iii-Nui.s in coinpari.'ion with Culex Larva, .... 20. Half-^rown Larva of Anophele.s tnaculipennis, 2L Full-f^rown Jiarva of Anopheles maculij>euuis, showiiif^ lu'a«l up.sidt' down, with t. Head of Full-f^rown Larva of An(>j)/itles j)nu(tij/euii.is, 2ti. Anopheles pU7ictipennis, iuliilt female, 27. Aiii>pheles punctipennis, adult male, from .side, 25. .l//oy>/H7<'.v c'rMf,'/«7i.v, adult female, .... 2J>. Auojiheles anjyritarsis, ii{\vi\i fe\ni\\e, ;W. Stegomyia fasciata, adult female, .... 3L Stegomyia fasciata, adult male, .... 32. Htefjonii/id fdscidid, adult male, from side. 3;j. tSte(/()nii/i(i ftisiiiifd, l)ody scales, .... 34. Jjarv.i and Pupa of lStt(ji>myid fascidtd, with enlarged part.s, ......... 35. Mouth-parts of Larva of f^tef/omi/id fdscidtd, . 3G. (Jrost; Section «)f Head and lieak of Mo.squito, showing Filiarias entering Heak, ..... 37. I'sorojj/iord rilidtd. adult female, .... 38. Females of Pso/ojihora cilidtd at rest on side wall an< «'»'iling, ......... :t!l. Malt- of l^sinophoKi lilidld, fron: side, 111. VoMiii.; L.irva of I'sunijihoni elow the surface, and their food is composed of all sorts of floating particles, and in the case of some of the larger forms they may even bite aquatic vegetation. They are rapid breeders and pass the pupal condition also in the water, but floating normally at the surface. In the pupae they breathe not from a breathing tube at the anal end of the abdomen, but from two trumpet-shaped tubes issuing- 1 2 MOSQUITOES from the toj) of the thorax. The thorax of all is much swollen, and with all pupfe the bodies seem lighter than air, so that they float at the surface without exortiou. The j)iip{E, however, arc active — sometimes very active. The abdomen, with anal par-like flaps, may be quickly ami violently agitated so as to draw them down below the surface, when it becomes necessary to escape from a fish or from some predatory aquatic insect. This great activity is necessary for the preservation of species, since stagnant pools abound with carnivorous forms of life, and such a little, fat morsel as a mosquito pupa, if it always stayed quietly' at the surface, would stand no chance. "When one tries to catch a pupa with his thumb and forefinger, at even the approach of the hand it disappears like a flash, rising slowly to the surface again when the active movements of the abdomen cease ; that is to say, when it gets tired or when danger ceases to threaten. All mosquitoes, so far as known, are ratlier rapid breeders. They pass through several generations in the course of a j^ear, and hibernate in both atlult and larval stages. Over-wintering mosquitoes may frequently be found in the cellars of houses, in cold garrets, in barns, under the lids of water-tanks, under bridges and stone culverts. In the extreme Southern States many mos(iui- toes are active all through the winter, and in most tropi- cal regions they may breed all the year round. In dr}', tropical regions, however, they breed only through the rainy season, and in the dry spell the species is perpetu- ated by the persistence of the adults, which either remain active, or more usually rather inactive or dormant, just ^•^ / \ \ / \ s Fig. 1. — Common Atljiiilic Coast " wini^-Ifgged " Mo.s(iuilo {Ciilex solticitans) ; giyatly enlarged. (Author's illuslratioii.) 4 MOSQUITOES as tliou<2:li they were liil)eriiHtinf;". In such diy spells the males geuerally die and the gravid females live over. This is also the case in winter hibernation in the north ; females are, as a rule, impregnated when liil)ernati()n time comes, and the}' live until the ice melts and the weather becomes of the proper temperature for the laying- of eggs. As shown by recent observations by Mr. J. Turner Brake - ley and Dr. John B. Smith, larvte, on the approach of Avinter, may be frozen up in the ice and when thawed out resume their growth, so that many undoubtedly hibernate in this wa3\ Parthenogenesis Among Mostjuitoes. We have just stated that tho males impregnate the females and then die during the early winter or during the early part of the dry spell in tropical countries, but there is evidence that parthenogenesis, or virgin birth, sometimes occurs with mosquitoes, as it does with so many of the lower forms of life. Professor V. L. Kellogg, of Stanford Univei'sity, reared in a covered jar, from the i)upa a female moscpiito which almost immediately laid eggs. There was no other mos- (juito in the jar and certainly no mating. From these eggs there hatched larvae, which grew very slowly and nearly reached full growth before they died. None of them succeeded in reaching the pupa stage. It is possi- ble that they died on account of their abnormal birtli, but there is also the possibility that tlu\v died from lack of proper food, and that under other conditions adults MOSQUITOES IN GENERAL 5 mig"lit have been reared. Professor Kellogg's observa- tion indicates plainly that interesting- studies can be made with mosquitoes in this direction, and it will be especially interesting- to observe the sex of the adults reared from wig-giers of virgin birth. How Long can the Larvae Live Under Water? In observations which I have made upon mosquito larvse of the g-enus Culex, I have been unable to time them below the surface for more than two minutes. As a rule they return to the surface to breathe after the expi- ration of not more than a minute. With the larvae of Anopheles, as will be shown later, the case is different. Although the larvae remain at the surface of the water during- the early part of their lives, when they become full grown they will descend to the bottom and mouth over the slimy grains of sand or water-plants which are to be found there. In this operation they have been timed by one of my assistants. Miss Sullivan, and remained ten minutes before ascending- for air. It seems also, from observations made by Dr. John B. Smith, that even Culex larvae may stay below for a longer period than I have observed. In the Fmtomological News for March, 1901, he states that he has timed them under water for as long a period as ten minutes, and in a later publication states that these same larvae which were Culex pungens which had been taken in ice, remained under water for fifteen minutes and more. MOSQUITOES How Long- may the Larvno Live? Professor Kellogg' reported an interesting series of ob- servations in the Entonwlogical Ntws for April, 1899, in which he shows that eggs were laid by a mosquito in his laboratory August 9th. (The eggs, by the way, were laid at 4.30 in the afternoon, a novel fact in itself, since it has been sui)posed that they were only laid after dark, and presumably usually in the dark hours of early morning.) These eggs hatched October 10th, and were kept alive in a jar of water at a temperature of from 50'' to 75° F. under normal conditions as regards light. They grew in size verj^ slowly and one after another died. But the sole survivor lived until February 16th, when it died at the ripe old age of four months and a week. None of them reached the pupal condition. As mentioned above, Pro- fessor Kellogg thinks that their death may have been due to the fact that their mother was a virgin and the slowness of their growth may have been due to lack of proper food and water. We have stated above that mosquitoes hibernate in the adult condition. That has been a matter of common obser- vation and has been a generally accepted fact. I have always sui)ii()S(>d it to l)e the only mode of hibernation, but an observation by Mr. J. Turner Brakelcy, of Hor- nerstown, N. J., made during the past winter, indicates that they may occasionally jiass the winter in the larval condition. Dr. John B. Smith wrote me, under date of January 30, 1901, that Mr. Brakeley went out into the MOSQUITOES IN GENERAL 7 marshes and collected a considerable number of the leaves of the pitcher plant {Sarracenia) filled with a solid mass of ice. He brought them into the house and thawed out the contents, and as a result sent Dr. Smith two bottles of very lively mosquito larvse. It seems that the temperature of the marshes had been 21° F. below zero and everything had been frozen solid for some time. Mr. Brakeley wrote that the larv?e were embedded in dif- ferent parts of the ice, and that in looking through the ice you could see the insects. He sent over one hundred of these thawed-out larvae to Dr. Smith, who stated that they reached him in good condition and that they lived, moulted, and grew thereafter in his laboratory. Adults issued in March and proved to be Culex pungens. The great numbers in which these larvae were found, suggests to Dr. Smith that larval hibernation must be extremely common, not only in New Jersey and in pitcher plants, but elsewhere and in other accumulations of water. The observations are of extreme interest and importance. How Long can the Larvae Live Out of Water? The fact that these insects remained dormant when frozen up in ice for an indefinite period, from the obser- vations of Mr. Brakeley, might at first seem to indicate that the theory which has been advanced, that when their mud-bottomed breeding-places dry up they remain alive in the earth, is in a measure substantiated. But, in reality, it has little bearing upon summer temperature conditions. Experiments which I have tried on a small 8 MOSQUITOES scale in g'l'iss vessels have shown that the larva; of Culex ■will exist for some little time in wet mud and tliat some of them will successfully transform after w atci- has been added, but in no case were we able to revive larva' in mud from which the water had been drawn off for more than forty-eight hours, and after twenty-four hours only a small proportion of the larva; revived. These results accord very accuratel}' with those reached by English observers in Africa, and, in fact, accurate ol)servations have not carried the larvne out of water alive for more than forty-eight hours. The im]iression to the contrary has probably been gained from oljservations on })ools which in reality did not entirely diy u]). Mr. V. A. Sperry, of Chicago, has made observations upon a j^oud which dried up and in which he could find no dead larvae, but he writes that after a week it rained and as soon as the rain stopped he found the mosquito larvae all through the water as lively as ever, and they began to issue as adults in about a week from that time. Mr. Benjamin S. Pascal, of Newfield, N. J., has sent to me an account <»f observations of his own which indicate to him tliat mos- quitoes may breed in grass or moist eaith. In the summer of 1900, I watched a slowly evaporating pool with great interest. It contained a surface area of about twenty -four square feet, and was fed entirely l)y rain-water and surface drainage. It was well stocked with mosquito larva^, and after a long drought the Avater was observed to have evaporated almost entirely, only a small i)uddle remaining in tln^ centre, wliich contained at the outside only three or four cubic inches of water. It MOSQUITOES IN GENERAL 9 was dark in color, owing- to the drainage from a manure- pile near by, and when glanced at casually showed no signs of life ; but on dipping in a coffee-strainer it was found to be literally massed Avith nearly full grown mos- quito larvae, many hundreds of which had been brought together into this restricted place. Drying continued iTutil there was almost no water left, but before the larvae died, that is to say, about twenty-four hours after the water contents were estimated at from three to four cubic inches, there came a heavy rainstorm which filled the pond with water, after which it was seen to contain ap- parently its usual stock of mosquito larvae. From this observation we are able to estimate the usual happenings in a mosquito pool. As the water dries the larvae grad- ually retire to the deepest point, and after the pool is apparently dried up there is still enough moisture at this deepest point to keep the larvae alive a number of hours. That they may die, and that, as I believe, they invariably do die in the absence of all moisture and in a space of time which must be reckoned by hours and not by days, is evidenced by the laboratory observations mentioned above. Length of Life of Adult Mosquitoes. It is very difficult, in fact practically impossible, to estimate the normal length of life of the adult of any species of insect that flies. We may keep them in con- finement and count the few days of their life, but the conditions are abnormal and cannot be made perfectly 10 MOSQUITOES uorniiil. An insect in a l)roe(ling'-ca<2ro may dio in twonty- fonr lioni's, l)nt that does not mean that it may not live for weeks outside. (\>rtain insects die (|uiekly from frigdit nnder such conditions, or from violent efforts to escape. I once covered a very larg-e Yucca plant with g-auze netting- and placed under the netting about a hun- dred honey bees, in order to see whether the flowers of Yucca could be fertilized by bees. In twenty-four hours every one of the insects was dead, and yet we know that the honey bee is a long-lived insect. Such evidence as we have, however, shows that mosciuitocs are also long- lived. It seems that they cannot live many days with- out plenty of air. Dr. Veazie, of New Orleans, Avrites me that he has kept them alive with various substances for a month. AVithout water or food, the limit seemed to him, from his observations, to be live days for all va- rieties he tried. If therc^ is no water in the house he states that the mosquitoc^s will leave the house and seek water. He has seen them repeatedly go down into a pitcher or a glass, remain for a few minutes, and then Hy away. He thinks that they do that principally to get a drink, although he has found eggs in a glass of water and in pitchers. Mr. Mitchell, of Victoria, Tex., how- ever, writes that he ke])t a number of moscpiitoes in n box once, to see how long they could liv(^ on air, and that on the twenty-first day none had dic^l. Medical ob- servers in their ex])erimental work with the mos(piitoes of the genus Anojiheles have been able to keep adults alive under glass, by feeding them upon slices of banana or some other fruit, for weeks, the banana being renewed MOSQUITOES IN GENERAL 11 every three or fonr days. Dr. Woldert, of Philadelphia, has kept adults for two weeks or more in a bottle with a slice of banana, sprinkling- the gauze-covering- occasion- ally with water. He has even kept them for from fifty to sixty days, but this was in the fall of the year, and, as ■we have elsewhere shown, mosquitoes hibernate in the adult condition and the significant life-period of the adult is the summer period. We know that they will live through the winter, but we do not know whether, under normal conditions, those hatching- in the spring will live through even half the summer. There used to be a current idea that when a female mosquito sucks a full meal of blood she is never able to bite again, since it was thought that she is unable to thoroughly digest such a meal. This idea, however, has been completely exploded in the experimental medical work, and a more approximate estimate of the length of the adult life has been reached in this experimental medical work, than has been elsewdiere gained. The army surgeons who have been working on the subject of mosquitoes and yellow fever have shown, as, in fact, had Dr. Finlay be- fore them, that the same mosquito will bite and suck blood again and again, and Drs. Reed, Carroll, and Agra- monte have demonstrated that the yellow-fever mosquito will not convey the disease until at least twelve days have elapsed since the time when it bit a yellow-fever patient. In the case of Anopheles and malaria there must be an interval of seven or eight days for the proper development of the malarial organism in the body of the mosquito, before the disease can be conveyed through a 12 MO^SQUITOKS pimcture to a healthy individTiah The best we can do, theu, is to say tliat the adult mosquitoes live iudetiiiitely — certainly, under favorable circumstances, even in sum- mer, for several weeks — and that they may bite an indef- inite number of times. Observations by Fermi and Lumbao on Ciilcv pipiois in Italy led them to believe that this mosquito, after emerg- ing:, devotes itself to bloodsucking- and similar jileasant occupations, but that e^g-layin.u' only takes place after from fifteen to twenty days, and that after eg-gf-layinii- tlie females die. This observation may be jierfectly correct, but it is contrary to the customary rule with insects, since it is almost a law that after the issuins: of the adults the first and main business of life is the luTpetnation of the species. Transformations of INIosquitoes Artificially Hastened. In thci summer of IDUO, while engaf^^ed in making- experi- ments as to the insecticidal effect of creosote-oil poured upon the surface of water in breeding- -jars containing- mosquito larva), I made what seems to me to be a most interesting observation. In one battery jar containing three quarts of water, eighty nearly full grown larv;e of CUih'.r sfimnJiinii and (\ prrfurlxins were i)l:u'ed, and one- fourth of an ounce of creosote-oil of a si>ecific g-ra vity 1.035 at G0° F. was poured. This was jar No. 1. In another jar were two quarts of water in which were placed 150 larva? of the same species, all full grown or nearly so. Upon this water, three-sixteenths of an ounce of a some- MOSQUITOES IN GENERAL 13 what heavier creosote oil was iDOured. This was jai- No. 2. When at -4.15 r.M. the creosote was poured in jars 1 and 2, no pupae were observed, but all larvse were full grown or nearly so. After fifteen minutes ten pupje were observed in jar 2 and five in jar 1. Ten minutes later fifteen were counted in jar 2 and thirteen in jar 1. Twenty minutes later there were nineteen in jar 2 and twenty -two in jar 1. Fifteen minutes later still there were nineteen in jar 2 and twenty-two in jar 1. Thirty minutes later there were seventeen in jar 2 (two having- died in the interval) and twenty-eig-ht in jar 1. As above stated, over nig-ht a num- ber of adults issued, ten in jar 1 and eight in jar 2, and twenty-four hours later ten more adults issued in jar 1. It must be remarked that the full grown larvae struggled violently on perceiving the uncomfortable presence of the creosote, and as they were just ready to transform, this violent struggling evidently assisted in the breaking of the larval skin, leaving the pupa bare. This transforma- tion from larva to pupa is hardly as interesting as the rapid development of adults, eighteen of which issued within fifteen hours after transformation to pupa, whereas j)reviously the shortest duration of the pupal state which we had observed was forty-eight hours. It looks like an effort of nature to perpetuate the species in the presence of a unique emergency. Mosquito Songs. Probably owing to an association of ideas, the curious sound made by mosquitoes as they approach one's ear is 14 3I0SQUIT0ES to most people extremely initatiuji;-. This faiut souuci will wiikeu many from the soundest sleep. It is not loud, and in (piality may perhaps best be compared to the dis- tant note of a bagpipe. The sound is apparently pro- duced, as with Hies and other dipterous insects, not by the rapid vibration of the wings, but by the vibrations of a chitinous process in the large trache.e just behind the thoracic spiracles. These vibrations are produced by the air during respiration. Dragon-flies and bees, as well as flies, sing in this way. With bees, however, the rapid vibration of the wings causes another hum, and the two notes are most readily distinguished, the wing tone of the honey bee being A', while the breathing voice is at least an octave higher, and sometimes nine or ten inW tones higher, going to B" and C". The exact musical note of the difterent species of mosquitoes seems not to have been investigated, but as long ago as 1874, A. M. Mayer, in the course of his researches in acoustics, made some most in- teresting experiments with the supposed auditory appa- ratus of some species of Culex, which, unfortunately, Avas not named. Mayer established the fact that some of the antennal hairs of the male mosquito are auditory. With tuning-fork experiments he showed that some of the hairs are especially tuned so as to respond to vibrations num- bering 512 per second. Other hairs vibrated to other notes. He also experimented with the song of the female, and showed that the auditory hairs of the male antenune vibrate when the song of the female comes at right angles to them. If the song is directly in front of the head it will be most fully perceived by the hairs. If the song of MOSQUITOES IN GENERAL 15 the female affects one auteuna more than the other, the male turns his head until both antenu* are affected, and is thus able to determine the exact direction of the female, to Avliich he then Hies. Mayer found that the male can thus g-uide himself to within five degrees of the exact direction of the female. His conclusion is that " these insects must have the faculty of the perception of the direction of sound more highly developed than in any other class of animals." Mayer carried his experiments farther, and made large wooden models of the hairs, with which he conducted interesting- experiments. His paper is published in full in the American Journal of Science and Arts, vol. viii. (1874), pag-es 89-103, and should be read by those interested in this subject. Recently, Mr. A. DeP. Weaver, an electrical engineer of Jackson, Miss., wrote me that while engaged in some experiments in harmonic telegraphy, in which a musical note of a certain pitch was produced by electrical means, he was amazed to find that when the note was raised to a certain number of vibrations per second, all mosquitoes, not only in the room where the apparatus was, but also from other parts and from outside, would congregate near the apparatus and would be precipitated from the air with astonishing force, striking- their bodies ag-ainst the apparatus. He states that he therefore covered a large surface with sticky fiy-paper and after sounding the note for a few seconds captured all the mosquitoes in the vicinity. He then devised an apparatus to electrocute them. A section of wire window screen with the paint removed was mounted on a board and small pins were IG MOSQUITOES driven between the meshes, the heads eoiuiii^- tlush with the surface of the screen. All the i)iiis wvw. connected tos"ether electrically, the whole forniin"' one electrode of the secondary coil of an induction coil, while the wire screen formed the other electrode. An alternatinf? cur- rent of hi.^h potential was then passed and when the note was sounded the insects precipitated themselves aii'ainst the screen and were immediately electrocuted. Mr. Weaver, unfortunately, does not state whether males only were captured in this way. His letter was an extremely interesting one, and surely his stick}' Hy-paper experiment suggests that further experimentation in this direction would be worth while. Apropos to the difference in the musical note of diti'er- ent kinds of moscpiitoes it should here be stated that, as will be pointed out in our eonsideration of the malaria- bearing mosquitoes of the genus Ano])lieles, the sound made by the female Anopheles is distinctly lower in pitch than that made by the less harmful mosquitoes of the genus Culex. An interesting parallel to this is tlu^ fact that the villain in the play has usually a l)ass voiee! How Far do Moscjuitoes Fly? Are Tlu\v Canifd ])y Winds? A very imi)ortant point to be considered by persons who are engaged in externnnation work against mosipii- toes is the one suggested by the heading of this section. To the owner of a large estate it is most discouraging to anticipate that at the close of careful remedial work, in 3I0SQUIT0ES IN GENERAL 17 which the di-aiiiage of breediiio -places and kerosening- of breedmg--pools has been carried on, hungry swarms of mosquitoes nuiy tly in from a distance or may be carried in by winds, to camp upon his grounds and in his house and renew the annoyance of the irritating- punctures, and perliaps even to seek out some neglected breeding-place and start new generations. Therefore the question of the length of flight is a most important one. In the summer of 1900, Mr. W. J. Mathesou, living at Lloyd's Neck, Long Island, a spot formerly infested by mosquitoes to an ex- traordinary degree, by intelligent exterminative measures succeeded in practically stopping' the breeding of mos- quitoes upon this rather narrow neck of land. It resulted that his house was mosquito-free until toward the end of August. Then, after a gentle and continuous wind of two or three days' duration, specimens of another kind of mosquito put in their appearance in large numbers. The explanation was obvious. These mosquitoes had flown across a strip of water forming one of the entrances from Long Island Sound to Oyster Bay, for a distance of a mile or a little more, aided by the gentle and continu- ous wind. This incident points out an important condition of afi'airs. Ordinarily, it may safely be said that mosqui- toes do not fly far. Where there is water favorable for egg-laying in the immediate vicinity of the place of their birth, and especially where there are warm-blooded ani- mals upon which they may feed, they have no migratory incentive. Then again, they are not strong fliers, as in- sects go. It seems perfectly certain, from the evidence 18 MOSQUITOES which has beeu collected, and especially by that adduced by Mrs. C. B. Aaron in her essay in the little book en- titled " Dragon-Hies versus Mosquitoes " (The Laniborn Essays, Appleton k Co., 1890), that mosquitoes are very careful not to take wing- during a strong breeze. Mrs. Aaron's words are worth (pioting : The migration of iiiosiiuitocs lias been the souree ol iimcii mis- apprehension on the i)art of tiic pul>iic. Tlic idea prevalent at our seaside resorts tliat a iaiiil breeze brings the swai'iiis of mos- quitoes from far inhmd, is based on the supposition that this in- sect is capable of long-sustained flight and a certain amount of battling against the wind. This is an error. M<>s(jiiitties are frail of wing ; a light puff of breath will illustrate this by luiri- ing the helpless creature away, and it will not venture on the wing again for some time after finding a safe harbor. The preva- lence of mosquitoes during a lanil i)reezeis easily explained. It is usually only during the lulls in the wind at such times, that Culex can lly. Generally on our coast a sea-breeze means a stiff breeze, and during these even the Odonata, and oft<'n the robust and venturesome Tjibanidse, will be found hovering on the lee- ward side of the houses, sand-dunes, anil thick foliage. In the meadows south of Atlantic City, N. J., large swarms of Culex are sheltered in the dense grass or wind-battered tree-tops on the off side of the sand-dunes. Here, in common with all localities so exposed to searching wind, the trees and large bushes are nnich stunted in growth and battered down to a flat top and common level by the wind. In these matted l)raii('lies, dense witli the close-clustered foliage, the mosquitoes may l)e discovered in such numbers as to Ijring ilespair to the heart of the student who is plotting their final extermination. While tiie strong bri'czcs last, Culex will stick close to these friendly slu-ltcrs. though a cluster MOSQUITOES IN GENERAL 19 of houses may be but a few rods off, filled with unsuspecting mor- tals who imagine their tormentors are far inland over the salt meadows. But if the wind dies down, as it usually does when veering, out come swarms upon swarms of the females, intent upon satisfying their depraved taste for blood. This explains why they appear on the field of action almost immediately after the cessation in the strong breeze ; on the supposition that they were blown far inland, this sudden reappearance would be un- accountable. Many observations made by the writer and by his cor- respondents support these views which Mrs. Aaron has expressed. Mr. W. C Kerr, of Staten Island, an excellent observer, is strong-ly of the opinion that mosquitoes are not blown over from New Jersey to Staten Island. Pro- fessor Herbert Osborn, formerly of Ames, la., has noticed that in dry seasons small pools within a quarter to a jialf a mile from the college buildings at Ames, dry up, and the mosquitoes disappear, in spite of the fact that within about a mile there are large pools which never become dry. One of my former assistants, Mr. R. M. Keese, found in Baltimore that by treating breeding-places a hun- dred feet or a little more from his house with kerosene, the supply of mosquitoes in his house was greatly re- duced, although there were many other breeding-places only twice as far away. Dr. John B. Smith, a well known entomologist, has recorded his observation that mosqui- toes will not rise or take flight wlien a brisk breeze is blowing, and that even a com'paratively slight breeze will keep them from the upper stories of houses. Dr. H. T. Fornahl, however, after several summers' 20 MOSQUITOES work ;it the Cold Spiiiii;- H;ul)or Laboratory, on Long Island, has stated that with a south breeze, especially after a prolonged and ^enth; wind of live or incjre hours' duration, mosquitoes become very troublesome and it is the local supposition that they are carried from the south shore of Lon<;- Island, fifteen miles away. This is, the writer tinds, the g-eneral opinion at several points on the north shore of Long Island, but observations which he has made on the moscpiito topography of that portion of the island have shown that there are usually many l)reed- ing-places much nearer than the south shore, and usually quite near the infested places, which will much more easily account for the mos(piito sui)ply. In fact, careful observations made by Mr. H. C. \\ eeks, of liayside, Long Island, have shown that in the immediate vicinity of the Cold Spring Harbor laboratories there are many breed- ing-places of such extent and such capacity as to indicate that the south shore theory nnist be abandoned. So many instances, in fact, have come to my attention, where extensive l)reeding-places ])rofusely stocked with mosquito larva' have been overlooked by the ])eoi)le of given neighborhoods, that I have, as a general rule, be- come more or less incredulous on the subject of extended mosquito flights. Fermi and Lumbao, in their report on operations in Sassari, state that the mosquitoes of the city do not go far from their original breeding-grounds, since they find sufficient food near the habitations of jieople and animals. The reason which the Itali;in authors give for this absence of migration may be correct or incorrect, but their experience has shown that where a house loca- 3I0SQU1T0ES IN GENERAL 21 ted near the centre of a city or villag-e is found to be in- fested by mos(initocs, search for the larvae shoukl be made in the house or near it, particularly in cellars or cisterns, in wells, in water-troughs, in sinks and tubs in the yard, and so on. The truth is that people do not take the trouble to make the careful search, and prefer to jump to the conclusion that the mosquitoes have flown in upon them from a distance. Mr. C. A. Sperry, of Chicago, writes that he is perfectly satisfied that mosquitoes are never distributed b}^ the wind. When the wind blows they are always on the ground, clinging to a support. They are seldom, if ever, seen as high as the third flat in the city. He further makes the sug-gestion that the idea that they are conveyed by the wind deters many people from making an eftbrt to rid themselves of the nuisance, which can so easily be accomplished. In one case, at a summer- resort on Long" Island, a man told him that the mosqui- toes came there from New Jersey, while not two hundred yards from his house was a pool that in Mr. Sperry's opinion produced all the mosquitoes that were such a troublesome pest and drove hundreds away from his place. Mr. Sperry is a close observer of mosquitoes and has studied them for years. Dr. C W. Stiles, of Washing-ton, however, is inclined to take a somewhat opposite view from Mrs. Aaron. He informs me that it has been his experience, at his summer cottag-e on the New Jersey coast, that mosquitoes bother his family only after land l)reeze-s have continued for sev- eral days. The cottag-e is situated about one-third of a mile away from the woods, toward the sea and within one 22 MOSQUITOI'JS huiulred yards of tlio surf. As it is al)Soluti'ly isolated from trees, and as the mosquitoes do not appear during: a lull in the breeze, but only after several days of land breeze, it appears to him that the popular view of the intluence of land breezes upon spreadini;- mos(piitoes sea- ward is not wholly without foundation. All the evidence so far adduced refers to nior(> or less normal conditions and, in fact, such conditions are the only ones which need i)racticalh' bo considered. Under very exceptional conditions, however, it seems i)erfectly plain that mos(piitoes may mi.^rate for considerable dis- tances ; two such instances are described in the following lines quoted from a recent letter received from the Hon- orable J. D. Mitchell, of Victoria, Tex., a reliable ob- server and a naturalist. . . . I have witnessed, in my life, two mip:rations of mos- quitoes, that will always I)e fresh and vivid in my memory. Where the Colorado River emjities into Matagorda Bay, a marsh is formed over the lowlands, ))y a raft in the river ; this marsh contains about eighteen square miles, and is a magnifi- cent breeding-place for iiiosciuitocs. I used to ranch it on the peninsula-like body of land, formed by Carancahua Bay on the east, Matagorda Bay on the south, Keller's Bay and ('reck on the west, and the Calhoun ( 'onnty north line on the north (ref«'r to <*oast maps of Texas). Tiic dis- tance between my ranch property and the niarsli al)(>ve described is, by bay route, about forty miles ; the way the crow Jlies, about thirty-five miles. My ranch was situated on Carancahua Bay, near the north end of land. The first migration occurred in ()ctol)er, 1S7!». There had been an overfU>\v from the upper country, which lilled the aforesaid MOSQUITOES IN GENERAL 23 marsh, but the balance of that section was very dry and needing rain, and there were no mosquitoes. A fairly strong easterly wind had been blowing for three days; on the evening of the third day the mosquitoes arrived, flying high, about fifty feet, and looking like a cloud or mist coming over Carancahua Bay. At the ranch they set everything on fire that had blood in it, and all work was suspended Ijy unanimous consent. Cattle and horses rounded-up milled continuously ; all work stock was turned loose as quick as possible and they went to the round-ups at full speed, and little or nothing was done for nearly five days ; l)y this time the main body had i^assed, though plenty remained to make everything uncomfortable for about two weeks. This migration was from east to west and the line was about three miles wide — above and below this there were no mosquitoes. Migration No. 2 occurred in October, 1880. They came from the same marsh before described — this migration confined itself to the Matagoi'da Bay shore line, reaching inland about half a mile ; there were as many mosquitoes in this limit as there were in the three miles of migration No. 1. They clouded the sky, bent down the grass with their weight, and made all driftwood and ground the same color. All stock left the shore and went north outside of the line of marsh. The wind was light and from the south, and did not affect the mosquitoes in their flight, which was westward ; the main flight was low, ten or twelve feet high and always in the same direction. With three other men I rode into the swarm to a large pile of drift and trash and set it on fire, and stood in the smoke for some time watching them. They passed sometime during the third day, leaving very few stragglers be- hind. By inquiry, I traced both of these swarms from the marsh before described to fifteen or twenty miles west of my ranch, a total distance, air line, of fifty or sixty miles. No. 1 crossed Trupalacios Bay, wliere it was five miles wide, and Carancahua Bay, where it was one mile wide. No. 3 holding to 04 MOSQUITOES tlie shore lino, crossed Trii|)aIacios Hay, tliree miles, Caraiicaliua Bay, at Pass, :500 yards, Keller's Bay, at Pass, halt' mile, Cox's Bay, one and a half miles, and ]^)rt Lavaea Bay, tour miles. It may incidentally be stated that malarial mosquitoes of the genus Anopheles seem much loss capable of ox- tended flight than the commoner mosquitoes of the genus Culox. Dr. V. A. Young, of the British Ainiy Medical Service, on his way home from Shangliai, Avhore he had been conducting experimental work against malarial mos- quitoes, called on me in February, 1901, and stated that it was his firm conclusion that, as a rule, Anopheles will not fly over two hundred yards, and that a breeding-place more than two hundred yards from the house will not suj)ply malarial mosquitoes to that house, provided there are other houses nearer. He mentioned a number of cir- cumstantial instances supporting this view. Christo- phers and Stephens, however, in their reports on the malarial expedition to Sierra Leone, state that it is cer- tain that under some circumstances Anopheles may fly much greater distances than has been sujiposed. In one small inland hous(^ which had been occnpiod by one old man, five or six Anopheles were to be caught each morn- ing. These were fr(^shly hatched and could only be de- rived from a brooding-place throe to four hundred y:irds away. In another place the same writers show a flight of six hundred yards. But, aftcn- all, what are even six hundred yards ? In an effort to free a locality from ma- hiria such distances become insignificant. On the whole, it seems to the writoi- tliat in almost no MOSQUITOES IN GENERAL 25 cases need an individnal or a community be deterred even for a moment from attempting- remedial work against mosquitoes by the idea that the mosquito supply is likely frequently to be renewed by flights from long distances or even from distances of much more than a single mile. A far more serious source of re-establish- ment of the mosquito sui)ply will be considered in the following section. Carriage of Mosquitoes by Railway Trains and other Conveyances. That mosquitoes are carried by railway trains must be a matter of common observation to everyone who travels. That this method of distribution is and has been a very important one, has, however, been rather g-enerally over- looked. It is said that mosquitoes were unknown in Hawaii until brought over in sailing vessels from the United States. On these sailing vessels they had proba- bl}'^ bred more or less continuously in the water-barrels, and when once introduced into the islands they bred Avith g-reat facility in the swamps and freshwater ponds, and to-day these insects are said to be very abundant there. Beyond the statement which occurs in Nuttall's mono- graph (1890), where the probable influence of Avinds, rail- ways, and ships in the dissemination of mosquitoes is briefly mentioned, the subject had received practically no consideration until it was brought out in the liulletin en- titled, " Notes on Mosquitoes," prejiared by the author and published by the United States Department of Agri- 26 MOSQUITOES culture, iu Aug-ust, 1900. It Wiis there stated that by means of railway trains unlimited quantities of mosqui- toes are carried unlimited distances, and on emergin^: from the cars they start to breed, even where mosquitoes are ordinarily rare, or would be rare under ordinary con- ditions. In this way, even mountain-resorts were said to get their supply of lowland mosquitoes, and the con- stantly^ increasing danger of this method of distribution, through the perfection of the railway service and the in- crease in the number of through cars, was pointed out. It was shown that although the State of New Jersey, as an example, has a bad moscpiito rei)utati(ni, that does not necessarily mean that there are any more breeding-places in the interior of the State, or that New Jersey mosqui- toes are any more prolific than elsewhere. The constant abundance of mosquitoes in New Jersey seemed to the writer to be dependent upon the fact that the coast is lined by many swamps, and that all through the summer evenings many trains are started inland from nearly a dozen points on the coast, from "Weehawken to Cape May. These trains may contain mosquitoes by the hun- dreds, and at every stop they may Hy from the cars and seek breeding-places near the railway. A discouraging feature of this method of spread is that although exterminative work of the most thorough char- acter may be carried on in any locality near a railroad, new supplies of mosquitoes are constantly being brought in and will begin to breed wherever water can be found. I called attention to the fact that in tlu^ Catskill Moun- tains one place which had come under my observation 3I0SQUIT0ES IN GENEUAL 27 was free from mosquitoes, until tlirongli cars on the railroads brought them up from the vicinity of New York City. After the publication of this bulletin some doubt was expressed by the newspaper reviewers of the importance of this method of dissemination ; but confirmatory evi- dence of a striking' character has since been gained, al- though, as a matter of fact, the proposition was so self- evident that it did not need confirmation. The interest- ing community work undertaken ag-ainst mosquitoes by the city of Winchester, Va., and which will be referred to in detail in the chapter on remedies, has brought out the fact that Winchester was at one time a favorite summer- resort, and that mosquitoes were practically unknown, but that with the estal)lishment of a night train on the Balti- more & Ohio Railroad, running from Camden Station, Baltimore, in the summer-time, mosquitoes began to be a positive annoj^ance in Winchester. Unfortunately, with the establishment of this night train, or about the same time, Winchester extended its system of water-Avorks and did not build sewers. As a result, with the arrival of the mosquitoes from Baltimore there was a plentiful KU])])ly of standing water all through the city, and conditions were thus perfect for the (levelo[)ment of mosquitoes in enormous numbers. Mr, C. A. Sperry, of Chicago, who formerly lived in Mexico, has informed me that in the City of Mexico, be- fore the railroads won? built to Tamjiico and Vera Cruz, there were no moscpiitoes. They were brought u]i from the coast, however, in the cars, and established them- 28 J/()S(Jl'J'J'(}h'S selves there. Tjuupico iiiid Vera Cruz, both low-lyiiisr cities, had always had moscinitoiis in immbers. The City of Mexico, lyiii^' on a ta])le-land 7,000 feet above the sea- level, and with a cool and pleasant climate, havin^;- no mosquitoes, thus with the addition of railroad facilities became infested. Mr. (-. P. Tjouiislnny, government entomologist (jf the Cai>e of (lood Hope (in litt.), is responsil)lo for the state- ment tliat the railroads in Cape Colony have Ix'cn re- sit()nsil)h' for tiiking' moscpiitocs to many inland towns which before the advent of the iron horse were quite free from the pest. Another correspondent ^^ives the details of a i)re('isely similar introduction of mosquitoes into a hi^h lyin.u' Missouri town. In a simihir way, sta<4'e-coaclies are res])onsible for the spread of mos(piitoes. Grassi, the Italian investigator, states that he counted two liuiidred s])ecinieiis of Anoph- eles on the inside of a coach, durin.i>' a drive lastini^" two hours through iho ])lains of Capaccio, and the same observer has recorded the cMpture of malaiial mosquitoes in a railway carringH? travelling- fioni I'lorence to Berlin. (^)iieer IM.'ices in which IMoscpiitoes Bnn^d. In the re[)ort of the Liverpool School of Tropical Medi- cine's ^Malaria Expedition to Sierra Leone, it is st.-ited that inos(piitoi's were found breeding in the broken bot- tles wiii(di were placed upon the toi> of a stone wall to act as a rin ml. i/> frisi', and that they were found als<^ breeding in the dower vast's on tiu- tables in the houses 31 OS QUI TOES IN GENERAL 29 of European residents, the servants having- conscien- tiously changed the tlowers every morning-, but with a cor- responding- hick of conscientiousness omitted to chang-e the water. I have found them breeding- in an okl tin to- mato-can on the dumps in Washing-ton. Mr. W. P. Seal, of Delair, N. J., Avrites that he finds the larva? of mos- quitoes in rain-filled hollows in apple, maple, and other trees, often at a considerable distance from the ground. Mr. Pratt has found them breeding- in a hollow stump near Bladensburg. Mr. Perg-ande has shown that they breed in the closed sewers in Washington, entering- throug-h the perforated sewer-traps and emerging- through the same holes. Mr. Matheson showed me an old disused well which was covered with a board cover, but on lifting- the cover mosquitoes were found roosting- on the under side in large numbers. There was a crack in the cover sufficiently large to admit them, and they smelled the water below, worked their way throug-h the crack and bred in the old M^ell. They will breed in all water-tanks, and the cover must be absolutely tig-lit, since g-ravid fe- males are so strongly attracted by water that they will work through a crack which seems almost too small to admit their bodies. Dr. John B. Smith says that they are found in New Jersey in great numbers in the pitchers of the pitcher plants of the genus Sarraccnia. These statements refer for the most part, if not entirely, to the common mosquitoes of the genus Culex, which we assume to be comparatively harndess from the disease- carrying standpoint, but they indicate plainly that where one's object is to rid a house or a neighborhood of mos- 30 310SQU1T0ES quitoes, in orelcr to avoid their inittitiiij;- puiu-turos and to produce tlio condition of general comfort which the ab- sence of mosquitoes briug-s, no possible spot where water can accuniuhite shouhl be overlooked. The smallest i)os- sible collections of sta<,'-nant rain-water become breeding" places and may swarm with larvte. Mr. E. E, Austin, of the Liverpool Troi)ical School Expedition, has seen in A^'est Africa that discarded bottles, Swiss milk and sardine tins, and cocoanut husks, frequently swarm with larva\ while the water which accumulates in disused calabashes and other vessels lying- about outside of houses is used for breeding. Mr. 11. H. Pettit (13ul. 18G, Mich. Agric. Col- lege Ex}). Sta.), in a report on " The Insects of the Upper Peninsula of Michigan," Avrites as follows: "Land that is being cleared furnishes an ideal place for them to breed. Holes made in removing stumps and into Avliich water has settled are often fairly alive with wrigglers." He collected a large number of larva> and pupje from a hole which would hold only a small qiumtity of water, and bred adults from them. AVo have mentioned above that Dr. Smith has found them breeding- in the pitchers of the pitcher plant, and Dr. Henry Strahau, in the Jnunail of Tropical Medicine for August, 1900, shows that mosquitoes breed in Lagos, West Africa, in similar plants. In the summer of 1900, Mr. W. J. Matheson, of Lloyd's Neck, Long Island, after a most successful work, which iucludi'd the drainage or treatment with kerosene of every possible ascertained breeding-i)lace within a half mile or more of his house, in October, on g"oiug into his greenhouse, noticed three or MOSQUITOES IN GENERAL 31 four mosquitoes, and on lookiug- around for tlieir breediug-- place lie discovered it in a tank at the corner of tlie g-reenliouse, in which the gardener was in the habit of keeping- from thirty to forty gallons of cistern water, in order that it might be of the temjierature of the green- house. The tank was apparently full of mosquito larvae. On measuring out in a quart jar, and counting them, Mr. Matheson estimated that there were probably in the neigh- borhood of three thousand larvae. This is a very inter- esting instance as illustrating the point upon which we have just insisted, since, after the exterminating- work which had been done, these three thousand mosquitoes would have caused considerable annoyance to the house- hold, and might have given rise to the opinion that they had tiown in from an unknown distance. Mr. H. C. Weeks, in the Scieniijic American SKpi^lement for January, 1900, very forcibly puts one aspect of mos- quito breeding in the following words : " . . . a care- ful supervision by those whose study of the subject quickly enables them to detect, the dangers from old sources, as well as from new ones arising from constantly changing conditions, especially about the towns — the building of a railroad, the making of a drive, the block- ing of an outlet to water by the washings of a storm or the falling in of some excavated materials, the building- of a new house whose waste water is] not properly cared for, these and a hundred others are exigencies which re- quire an interest in the subject and a careful and minute watchfulness." Mr. Pergande's interesting discovery that they breed 32 3I.0S(jl'IT(>I<:S ill the closed sewers in AVasljin<,'-ton, deserves more de- tailed mention than we have given it. His house in northeast Washington being infested with mosquitoes autl uo exposed standing water occurring in the vicinity, he thought of covering the small perforated sewer-trap in his back yard with a wire screen. To prevent the pos- sibility of moscpiitoes entering the screen from the out- side, a layer of cotton was placed around the edge of the trap on which the screen rested. On August 2J:tli two females of Cnlcx j^ungais were found under the screen. September 3d another was found in the same place, but it went back to the sewer as soon as the rajs of the sun struck the screen. September Gth, lOtli, and lltli, five more were caught. Female moscpiitoes in search of breeding-places had evidently tlowu through the sewer- trap perforations, had found standing water in the sewer and laid their eggs, from which a generation of adults was developed. There are other localities in AVashingtou, far removed from the Potomac River front, where mosquitoes are more or less abundant, and where there seems to be no standing water in which they can breed. It therefore seems rea- sonably sure that this sewer-breeding may be rather com- mon in certain cities where the general slope is so slight that the water may almost stand still for a few days, in the absence of very heavy rains which tlusli the sewers. Of course such breeding will easily be stopped by a little neighborhood work, either by occasionally i)ouring a little kerosene down the sewer-traps or bj' covering them Avith a wire screen, as did Mr. Pergande in his experiments. 3I0SQUIT0ES IN GENERAL 33 Another instance of the necessity of searching- out of the way places for mosquitoes and larvis has recently been told me by Dr. James Carroll, U. S. A., a member of the Yellow-fever Commission. Visiting an army officer in charge of a post in Cuba, he found the yellow-fever mos- quito in numbers in the quarters. The officer in charge could not imagine where they came from, as, under orders, he had had every possible breeding-place exterminated, either by surface drainage or by petrolizing. Dr. Carroll noticed that the table in the dining-room had been insu- lated by placing its legs in small jars of water, the surface of the water being carefully covered with kerosene. In going into an adjoining room, however, he found that a table there had also been insulated in the same way, but that the water about only one of the legs of the table had been covered with kerosene, while the jars under the other three legs were swarming with mosquito larvge. This was the fault of the orderly, an Irishman, who liter- ally obeyed orders in kerosening such vessels as had been pointed out to him, but no more. Enough mosquitoes bred in these three jars to stock a large community. It is common opinion that mosquitoes do not need standing water in which to breed. It is generally sup- posed by non-observant people that they are able to breed in wet grass, and it is a common observation, as recently expressed by a correspondent of the Pacific Rural Press of San Francisco, that mosquitoes are more abundant about well watered lawns than in vacant lots, with the dry, sandy surface which they naturally have in a dry summer season. But there is not the slightest evidence 34 2£o;SQl'lT()ES that any such condition of affairs can exist. In such cases as that described by the Calif ornian, the mosquitoes are naturally attracted by the moist air. They search for breeding-places, and are attracted by moisture, however slijjfht ; and then, too, it is well known that they drink water, and while the drops on the grass blades will not induce them to lay eggs, they can readily fill their stom- achs in the absence of the more highly nutritive liquid known as human blood. Some men drink water instead of beer, but it is a sad fact that no mosquito is ever known to drink water when she can get blood. In the California case, the humidity of the air around the sprinkled lawn pleased the mosquitoes better than the dry air of the vacant lots, and in the face of the multifarious and unob- served Qpportunities for the collection of small quantities of water, many of which we have just indicated, there will always be found some exi^lanation for mosquito abun- dance, other than that they will breed in wet grass. There is this to be said, however, as has been pointed out more fully in another paragraph, that in dry seasons mosqui- toes will live until the rains come, and this is especially true of pregnant females. Nature cares for the pcri)ctua- tion of the species, and in some way provides for the ex- istence of individuals until the perpetuation of the spe- cies is assured. Food of Adult Mosquitoes. With little doubt it is only the females of mosquitoes which draw blood, and with as little doubt female mosqui- toes are normally plant-feeders. When we consider the 3I0SQIHT0ES IN GENERAL 35 enormous numbers in which mosquitoes occur, it is safe to say that only au infinitesimal proportion of them ever taste the blood of a warm-blooded animal. They have been seen with their beaks inserted into juicy })lants ; they have been observed sucking- ripe fruit, watermelons, and even boiled potatoes. There are in this country great tracts of marshy lands into which warm-blooded animals never find their way, and in which mosquitoes are breeding- in countless numbers. But they are not confined to plants and warm-blooded animals. They attack other insects, althoug-h observa- tions on this point are not common. Dr. H. A. Veazie, of New Orleans, informs me, however, that he has seen mosquitoes stinging- the Cicada, or " locust," as it is in- correctly called, and also the soft skinned pupa of the same insect. Dr. H. A. Hag-en has recorded an observa- tion where he saw a mosquito in the Northwest engag-ed in feeding- on the chrysalis of a butterfly. Cold-blooded vertebrates are also attacked. Mr. J. Turner Brakeley, of Hornerstowu, N. J., writes that he has seen a black ter- rapin surrounded by a swarm of mosquitoes, but that she paid no attention to them, possibly because she was en- gaged in egg-laying. Moreover, there are several in- stances on record in which mosquitoes have been seen puncturing the heads of young fish. That mosquitoes suck the blood of birds is also well proven. In the course of Ross's original observations in India with a malarial disease of sparrows, he had no difficulty in inducing- mosquitoes to l)ite these; birds, and a recent correspond- ent of the BaU'uHore Sun nearly lost some pet canaries 36 MOSQi:iTOES throne:]! the hitcs of mosquitoes, which seemed especially attracted to these birds. To revert once more to the plant-feeding habit, persons eng'aj^i'cd in the study of malarial relations of mosquitoes have found that they feed readily upon fruit, and bananas are a favored article of diet. Dr. John B. Smith, of llut- gers College, informs me that he has seen males and females of what is probably Cuhx soll/'citan.s attracted by the blossoms of wild cherry, and appear to dig into the centre of the blossom, at Anglesea, N. J. So abun- dant were thej^ that he captured hundreds by sweeping his net over the blossoms. The male mosquito seems to be exclusively vegetarian in its diet. The beak in this sex is weaker, and does not seem fitted for the penetration of the skin of even a tender-skinned animal. Its food it probably chiefly gained by sipping exposed liquids. They are often seen sucking at drops of water or molasses, or beer, or wine. Dr. St. George Gray, of St. Lucia, British "West Indies, finds that down there he can almost daily catch one or two males on the neck of a decanter, or in a wine- glass that has just been used. He has made some inter- esting observations on the intoxicating effect of wine upon the males. It appears from these observations and the beer-driidving hal)it of the males, as observed by Schwarz, that in any discussion of sex habits into which the mosquito may be lugged as an example that blot)d- thirstiness may exist in the female sex, this statement may be offset by the fact that even with this cr(^ature the male sex is the one that is prone to alcoholism. MOSQUITOES IN GENERAL 37 In spite of what we have just said about the non-pene- trating- mouth parts of male mosquitoes, Dr. C. W. Stiles informs me that he and Hurst (the author of an im- portant paper on the pupal stage of Culex, Manchester, 1890) made an observation in the summer of 1889, at Leip- sic, which convinced him that either the males do oc- casionally bite or that occasionally females possess feathered antennae. Stiles and Hurst were out in a row- boat one evening and were bitten a number of times by Culex nemorcdls. One individual which bit Stiles on the left hand was crushed, and in the crushing act a consider- able quantity of blood exuded — enough to make a fair- sized blood-stain on his skin. Upon examining- the dead body he was surprised to note that it possessed male an- tennae. Hurst also examined it, and remarked that it was the first instance he had known where a male Culex liad actually been caught sucking blood. Dr. Stiles tells me that Hurst intended to place the observation on record, but that he does not think it was ever i3ublislied. Dr. Stiles is so well known as an accurate observer, that some other explanation than faulty observation must be offered in this instance. This observation, although apparently without pre- cedent, leads to a decision coinciding- with that of Jor- dens (1801), who thought that tlie male mosquito could l)ite, and wrote, according to Dimmock, " But since the male is also provided with a sucking seta it is not com- prehensil)le Avhy it should not use it for the same pur- pose." Dr. Dimmock, in his admirable dissertation upon " The anatomy of the mouth-parts and of the sucking ap- 38 MOSQUITOES ])ai'atns of some Diptora " (1881), made a most careful stutly of the mouth-parts of both male and female mosqui- toes. His conclusions are decidedly against the possibil- ity that male mosquitoes can bite warm-blooded animals. Ho says, " I have tried to have the male moscpiitoes bite me when in the field where they were abinnhint, l)ut they did not seem attracted, as the f(>male mos(putoes were, to my person ; tho}^ flew away indifferently without lighting upon me. I have often taken male mosquitoes, Avitli all possible care to prevent disturbing them, IxMu^ath a glass cover on my hand, letting them remain long enough to be as trancpiil as they were when upon the leaves and grass of the field, but tliev would iieitliei- l»ite nor sliow any desire to do so, nor have I been al)le to feed male mosquitoes with water, saliva, or fresh blood, all of which liquids the females often drink with avidity. " Upon anatomical grounds, I believe that male mos- quitoes take liquid food, although I have never dissected their stomachs to see what this food was. They have mouth-parts and pharynx devel()p(>d sufHcicntly to suck liquids; but tlie al)sence of barbed maxilhe, of a frec^ hy- popharynx, and of (eso])hageal bull), lt>ads one to su])])ose that they take a smaller quantity of food tliaii tlic females do, and that they do not o1)tain it by piercing the skins of animals." There is a Euro[)ean s[>e('ies of mosquito, CuJe.r sid'nvis Ficalbi, which is said to \)o diurnal in its hal)its. and to live in salt water, of which tlu» male is said to bite, and to possess mouth-parts (juite like those of the female. BIOSQUITOES IN GENERAL 39 Abundance of Mosquitoes. In modern times everyone who likes out-door life, espe- cially men interested in bunting- and fisliing-, is able to tell mosquito stories which rival the somewhat rare instances which come down to us from ancient times. I have heard sportsmen, in fact, vie with each other in describing the abundance of mosquitoes in certain localities, but, familiar with the tendency of hunters and fishermen to indulge in the rhetorical figure known as hyperbole, as evidenced in the general acceptance of a specific meaning as applied in the expression " a fish story," or the adjective " fishy,'' one is warranted in a certain measure of disbelief. It is un- doubtedly true, however, that certain localities in this country are almost uninhabitable because of the great numbers of mosquitoes found there, many otherwise desirable neighborhoods do not improve for this reason, and some regions are absolutely unsettled on this ac- count. Professor E. AV. Hilgard, of the University of Cali- fornia, has written me that up in northern Washington, in the pine forests north of Spokane, the gray mos- quito, or Culex, seems to be the sole possessor of the land, and is a fearful nuisance, as in arctic regions. The first thing- on g"oing- into camp is to establish a close line of smudges above the wind, so as to enable the pack animals and the men to eat in comparative peace, but about mid- night the entire swarm is l)ack again. He states that there are scattered lakes in that region Avliere they breed, but they must migrate considerable distances. He further 40 MOSQUITOES writes that in INIoiitaua lio has s(U'n all tlu; workhorses in the field sheathed in sheets during- the day, and these were dotted with small blood spots. An ol)servation made by my colleag-ue, Mr. E. A. Schwarz, at Cori)us Christi, I have had occasion to quote several times. He says that at this place, when the wind blows from any other direction than south, "hundreds (read malaria had been suggested a number of times. The most forcible argument, however, was presented by Dr. A. F. A. King at Washington, Avith whom the idea was entirely original, in a pajx'r read before tlie Philosophical Society in 1882. The actiial demonstration, however, was not broug"ht about \\\\i\\ much later, and in this actual demonstration workers of several nations had a share. The researches of MacCallum, of Johns Hopkins Univer- sity, while investigating the malarial disease of the com- 48 MALARIA AND MOSQUITOES 49 mon crow, contributed greatly to the elucidation of a knotty point in the life history of the parasite ; the stud- ies of Itoss upon the malarial disease of sparrows in India jn'oved effectively the transmission of this disease by mosquitoes ; Avhile the experimental demonstration of the transfer of the parasite of human malaria by mosqui- toes was first performed by Italian investigators, al- thoiigh it has since been done many times in many parts of the world by workers of many different nationalities. The life history of the malarial parasite of human kind maybe briefiy summarized as follows: All of the mala- rial parasites are protozoans, that is to say animals — and not bacteria, that is to say plants. In the human blood these protozoa inhabit the red blood corpuscles and in the blood they go through a sporulating existence, which may continue indefinitely unless checked by quinine or in some other way. In the red corpuscle the parasite appears as an amoebula which gradually grows until it nearly fills the interior of the corpuscle, digesting appar- ently the red coloring matter of the blood and forming, as the result of this digestion, pigment spots in its interior. On reaching full growth the nucleus of the amoebula subdivides, each division gathering about itself a certain amount of protoplasm, until instead of the single amoe- bula the cor[)uscle contains a large number of spores. The walls of the corpuscle then break, and the spores are liberated into the blood serum. From a single infection this sporulation or liberation of the spores takes place practically sinniltaneously and marks the beginning of the malarial spasm. 50 jK^s^rrroh's The three dirt'erent kinds of iiiidaria, namely, that in which the fever recurs every two days, known as tertian malaria, that in which the fever recurs every three days, known as quartan malaria, and the severe autumn fever, known as jestivo-autumnal fever or tropical malaria — by far the most danf;erous of the three — are l)y some writers supposed to be caused by distinct species of parasites. This view is not held by other Avriters. But at all events, the period of development of the sporulating- stage of the organism ditiers in length of time. As is very well known, it frequently happens that the malarial fever or chill will recur every day. That means, in tertian mala- ria, that there has been a reinfection on one of the alter- nate daj\s, the development of the anuebulas being con- stant in i)oint of time, one set sporulating twenty-four hours after the other set. It is just as this sporulation occurs — just as the spores are liberated into the blood serum — just as the malarial spasm is about to begin, that the administration of quinine is most effective. It seems to kill the spores when they are liberated, but aju^ears to have very slight efi'ect upon the organism when it is enclosed in the red blood corpuscle. This sporulating develoi)ment, each of the liberated spores attacking and entering new red c(n'puscles, may continue as above stated indetinitely. ]>ut not all of the amoebulas undergo this d(!veloiunent. Some of them, so long- as they remain in the human body, apparent!}^ die and are digested by the leucocytes. When, however, these forms are taken from the human body, even when a blood sample is simply placed under MALARIA AND MOSQUITOES 51 tlie microscope for examination, they nnderg-o a develop- ment entirely ditt'erent from the sporulating- form. Some of them grow large, others put out slender filamentary arms, or tlagella, as they are called, which separate from the body of the organism and fuse with those which do not Hagellate. This is the true sexual generation of the parasite, the flagellating forms representing- the male sex and the receptive forms the female sex. The develop- ment up to this point will take place anywhere outside of the human body — in the stomach of mosquitoes of the genus Culex, or, presumably, of other biting insects, but it is onl}^ in the stomachs of the genus Anopheles, so far as observed, that a further development takes place. After the fusing of the flagella Avith the female germs in the stomach of the Anopheles moscpiitoes, the fertilized organisms attach themselves to the walls of the stomach, penetrate the inner walls, and locate themselves just under the outer muscular wall. They then rapidly increase in size until they eventually become five times as large as at first. They are now known as zygotes. Clear spaces begin to appear on the surface. These clear spaces are known as centromeres, and they are rapidly surrounded by minute short dark lines, which, when seen under a very high power of the microscope, are shown to be spindle-shaped cells, known as blasts. These blasts rapidly increase in number until eventually they till the entire zygote, obscuring the centromeres, and when this condition of affairs is reached the zygote bursts and the blasts are liberated through the muscular wall of the stomach into the body cavity of the mosquito. They 52 MOSQUITOES are active and penetrate rapidly into the tissue of the salivary duct and so iuto the proboscis of the mosquito, and, with the saliva or poison, they enter the blood of the next warm-blooded animal which the mosquito bites. It is then supposed that tlu; blasts enter the red blood cor- puscles and the development re-be<^ins at the sta^e where we took it u]). It is thus shown that the full development of the mala- rial parasite cannot take place within the human body ; that the Anopheles mosquitoes are necessary secondary hosts ; that the sexual s'eneration of the parasite takes place only in mosquitoes of the i^enus Ano})heles ; and further, that the old ideas of malaria from l)ad air (and of course the word iiKilnrid means bad air), swamp '" miasma," and so on, are to the minds of those familiar with the subject of the biology of these low forms of life com- pletely overturned. Eeasoniiig- from the life history of the parasite alone, as observed, would not, however, satisfy the minds of ])eoi>le at large, and, in fact, it did not satisfy many medical men who were not esi)ecially familiar Avith this field of bio- logical research. Very many jjractical denumstrations have therefore been made. One of tlie most interesting was that carried on by Professor (irassi, the Italian, during the summer of 1900, in the Plain of Cai)pacio, near Salerno. The objects of this experiment were: (1) To atlbrd an absolute proof of the fact that malaria is trans- mitted exclusively by tlie bite of Anopheles mosquitoes ; (2) To found, on the results of recent lesearch, a code of rules to be adopted for freeing Italy from malaria MALARIA AND MOSQUITOES 53 in a feAV years. The experiment consisted in protecting- from malaria railway emplo3^es and their families, living in ten cottages, at the stations of St. Nicolo, Varco, and Albanella, situated along the Battipaglia-Reggio Fro. 4. — Experinientnl House Occupied by Drs. Sambon and Low on the Canipaii'na in the .Sumnier of 1900. (From the Journal of Tropical Medicine.) Railway. They nnnd)ered 104: ])orsons, including thirty- three children under ten years of age. Of these 104 in- dividuals, at least eleven, in(^ludiiig four children, had never suffered from the disease, not having previously 54 MOSQUITOES lived in a malo.rions district ; a certain number, it ap- peared, had not snffi^'ed from it in two or tliree years, and all the others, that is to say, the larsfe majority, had suffered frt)m it duriiiq- the last malarial season, some of them even in tin? winttn*. Durini;- the malarial season, the health of the protected individuals was s'ood, with the exception of a few cases of bronchitis and a case of acute gastroenteritis. None of these cases were treated with quinine. The 104 i)ersons, Avith three exceptions, had re- mained free from malaria up to Septend)er Kith, the date of the report. Another vcny strihin.Gf exp(n'iment which during- the autumn of li)00 was mentioned in newspa[)ers all over the world, was that performed by Doctors Sambon and Tjow, of the London School of Tropical IMedicine, in the Io- nian Cam])a^-na, during- the late summer and early autumn of 1900. They had constructed a comfortable little five- roomed wooden house about three hours' drive from Ostia, in one of the most malarious i)orti()ns of the Oampagna. The house was tightly l)uilt and was thoroughly screcMUHl. The experimenters lived in this house through tlie pciiod Avhen malaria is most i)revalent. They took no (juiuiue and no health precautions beyond the fact that at sun- down each day they entered the house and remained there until daylight the next morning. ])r Rees, of the London School, visited them and occupied the house with tliem for a portion of the time, and all three conducttul labora- tory work in one of the rooms, which was fully equipped for such a puri>ose, and led a l)usy and contented life. They visited the neighboring villages and investigated 3IALARIA AND MOSQUITOES 55 outbreaks of the fever in men and cattle. They received and entertained many visitors who were interested in the experiment. Thej^ turned indoors before six o'clock and then stood at the windows and timed the first appearance !#' Fig. 5. — The Maliiriu llousi' on llic ('imii)!i,<,nia, seen from a distance. (From the Journal of Tropical Medicine.) of Anopheles, which would come at a certain hour each evenino- and try to enter the screened windows and doors. As Dr. Rees expressed it, "It must have been very tanta- lizing: for them to be unable to get at us." When the rains set in, everyone said that that was the critical time 56 MOSQUITOES of the experiment. The jieoph' in tlu^ suriouiuling- coun- try generally became feverisli and ill, 'which meant simply that they were all full of malaria, and the chillin."- caused by the rain broug-ht about an exi)losion of the fever. The experimenters, however, went out into the rain and j^i-ot soaked to the skin, but their health remained perfect. Not the slirkeley were admirable, and he advises the following oHicial steps for greater New York: 1. Kecpiire malarial cases to be reported as scarlet fever and diphtheria are now. Malaria is at least as dangerous as scarU't fever ; economically it is far more of a scourge, for it atiects adult breadwinners as well as children. 2. Send an inspector to evi>ry inflected house, who shall instruct the people to kill all the Anoi)heles in the house, to provide the windows and doors Avitli screens, to isolate the patient with particular care from mosquitoes, and to cause all the standing water in the vicinity to be drained or heavily petrolized. liigid treatment with (piiniiie should be insisted upon and the drug furnished gratis to those unable to pay, as diphtheria anti toxine is now supplied. Dr. Berkeley believes that in a summer or two it would be i)ossible, by these measures, to reduce tlic nnmlxi- of local cases by more than ninety per cent. Another interesting case has Ixmmi r»>ported to m(^ by the Rev. Wm. Brayshaw, of (Mi.iptico, Md. Chai)tico is situated at the head of a wide-spreading bay or elbow of the Wicomico River, about eight mi]i>s from the point where this river enters into the Potomac at Rock Point. MALARIA AND MOSQUITOES 59 The tide is ordinarily about two feet at the fulL The vil- hisre rests between two hills of 80 or 90 feet elevation. The valley is almost flat, and consists of marshy pools, in which the mud or ooze can easily be pierced with a strong pole to a depth of several feet. Three of these pools or ponds are directly in the rear of the house known as the rectory, in which he resided with his wife on June 24, 1899. Neither of them had ever had nuilaria or fever before, but the mosquitoes were so numerous that it was impossible to take rest at night for a while. On July lltli his wife was taken with malaria, and on September 4tli had to be re- moved to the mountains. Mr. Brayshaw himself was sick most of the time, and every house in the villag-e had from one to five persons suffering- from malaria. He proposed ditching- and drainage, but there was no money, and every- body laughed at the idea, as many of the citizens had lived there from childhood to an advanced age. There did not seem to be sufficient fall to carry off the " effete matter." On May 19, 1900, he gained the consent of the property owners to ditch through their land a distance of 560 feet to Chaptico Creek. He paid for this himself. The expense was about $10. The result he sums up as follows : " During- the summer of 1899, from May to Octo- ber, the mosquitoes were so numerous that life was a burden during the night, and they Avere so small that nets seemed to have no effect upon them. From May to Octo- ber, 1900, quite a numl)er visited us, until June 12th, when they disappeared, and we were free from them until the last six days in September, when I found a local cause for their breeding-. In the summer of 1899 every house in the 60 3/en jn'oved that Anopheles transmits malaria, and that possibly this is the only method which has been proved, still insist that there may be, and even that there must be, other methods. As a matter of fact, it is practically impossible to prove that there is local malaria where there are no Anopheles. Tlie bite and method of attack of Anopheles is so insidious that these nioscpiitoes attract very litth^ attention wlnn^e tliey are not especially nunun-ous. One may be l)itten by them while asleep at night almost without realizing it. Anoph- eles may be present where there is no malaria, since it will always remain uninfected unless some vcu'tebrate ani- mal suffering with the disease comes to its neighborhood. 3IALAEIA AND MOSQUITOES 61 There was no autochthonous case of malarial fever for years at the League Ishuid Navy Yard, although there was a distinct breeding-g-round for Anopheles near by. Woldert has caught larvte of Anopheles in a clear pool of water in the Pocono Mountains of Pennsylvania, a notable health resort, at an elevation of three thousand feet above sea-level. The statements that malaria has prevailed when there were few or no mosquitoes are alwaj's too vag'ue to be of value, because it is not definitely stated whether the cases were relapses or fresh infections. In cases where mosquitoes are numeroiTS, moreover, and there is no mal- aria, to the point aaIiIcIi we have already made that prob- ably no malaria has been broug'ht into the vicinity may be added the fact that when mosquitoes are numerous, almost without exception they are found to be the com- mon species of Culex, which, as shown, have nothing to do Avith malaria. It is often stated, for example, that malarial fever is caused by excavating the ground ; newly turned earth is said to be responsible for it, but, as a matter of fact, as pointed out by Ross, there are millions of people constantly engaged in digging Avithout suffering from the disease more than do others, and then also ex- cavations always result in surface pools of water, m Avhich for a time Anopheles will frequently be found breeding. One curious case has been mentioned by Mr. D. E. Hutch- ings, in the English journal, Natiwe, in which he stated that he knew of a medically authenticated case of malaria having been caused by fresh earth carried past a window in buckets by coolies. This statement is criticized by Ross in the following words : " Which fact was medically 62 MOSQUITOKIS authenticiiteil — the fuct tliiit the piiticiit sntfeied from ma- laria, or that liis mahiria was caiised l)y the earth carried past in Imekets ? I can iiii(h'rstaiid the first being certi- fied to by a doctor, but scarcely the second. How did the doctor prove that the fever was produced l)y the earth in the buckets? It seems to me that the only way in wliich he could have done so in a trustworthy and scientitic manner would have been to infect a second person by having- the buckets carried past a second time. I doubt whether such instances — and we see hundreds of them in the press — will liear close examination." It has been claimed by Italian observers and others, that there is a A^ery exact coincidence between the geo- g'raphic distril)ution of malaria and Anopheles mosqui- toes. Bearing on this point, the conclusions reached by Nuttall, Cobbett, and Strangeways-Pig-g, in their studies in relation to malaria {Journal of //'/(jieiie, vol. i., No. 1, January, 1901), are very important. They are as fol- lows : 1. The disappearance of ague from Great Britain does not depend upon the extinction of mosquitoes cai)able of harboring the i)arasites of malaria. 2. Three species of Anopheles (^1. 'inaeullpenuis, A. hlfnroitus, A. nitirijws) are to be found in Great Britain in all districts Avhich were formerly malarious, but also in places concerning which there is no record of the former prevalence of ague. 3. The Anopheles to-day are most numerous in low- lying land containing many ditches, ponds, and slowly flowing water, suitable for their habitat, and correspond- MALARIA AND MOSQUITOES ^ ing" to the district.s where ague was formerly preva- lent. 4. Since the disappearance of ag-ue does not depend upon the extinction of Anopheles, it is probably due to several causes operating together : {a.) A reduction in the number of these insects conse- quent upon drainage of the land, this being in accord with all the older authors, who attributed the disappear- ance of ague largely to this cause. (Jj.) Reduction of the population in infected districts as the result of emigration, aliout the time when ague disap- peared from England. This would naturally reduce the number of infected individuals, and thus lessen the chance of the Anopheles becoming infected. (c.) It is possible that the use of quinine has reduced the chances of infecting the Anopheles, through checking the development of the parasites in the blood of subjects affected with ague. Of these, the tirst-mentioned cause seems to have been chiefly operative. The possibility is not yet excluded of there being another intermediary host besides man, capa- ble of harboring the parasite, and, assuming that this were so, this host may have become extinct in the low- lands where it is known that the fauna and flora have al- tered. 5. The coincidence of the geograi^hieal distribution of ague and Anopheles as claimed l)y Grassi for Italy, and as probably holding good for other parts of the world, is hereby disproved for England, and consequently the gen- eralizations are proved to be premature whereby he ex- 64 MOSQUITOES eludes other blood-suckiiii^' insects from being' possil)le hosts of nuilarial parasites on the strength of his sup- posed geographical agreement. G. Since the geogra})hical distril)ution of Anoplieles in England is wider than the fornu'r distril)ution of ague in that country, Ave are forced to conclude that it is not a matter of the geographical distriljution of Anopheles as much as of their numerical distribution. 7. Our observations having proved the existence of Anopheles in non-malarious districts, we believe that they will explain the occasional occurrence of ague in out of the Avay places, without making it necessary to assume that nndaria-bearing mosquitoes have been freshly im- ported, for, given suitable conditions of temperature and the requisite number of Anopheles, a malarious subject coming from other parts might well infect the local in- sects, which in turn would spread the infection to healthy persons. 8 We Avould suggest to those engaged in the investi- gation of malaria in other countries, that they search as carefully for Anopheles in non-malarious as in malarious regions. More data as to the number of these insects in various localities are certainly required, though we are fully aware that numerical estimates permit of a consider- able degree of error. Nevertheless, they would always possess a relative value. Grassi has repeatedly asserted that the geograi)hic dis- tribution of Anopheles in Italy coincides with that of inalaria, and on the strength of their wider geographic distribution he excludes a number of blood-sucking creat- MALARIA AND 3I0SQUIT0ES 65 ures, such as mites, ticks, stable-flies, gad-flies, black- flies, puDkie-flies, lice, bedbugs, and Culex, from being possible carriers of malaria. Probably nothing more need be said in regard to the general subject of malaria and mosquitoes. The case is abundantly proven, and it remains necessary from the health standpoint to know all about the mosquitoes of the genus Anopheles — how and where they live and breed, and how to distinguish them from other mosquitoes in all stages of their existence. All these facts will be con- sidered in Chapter IV. Ill Tlte Common Mosquitoes of tJte Genus Culex CULEX is an old g-eniis named by Linnajus in 1735, which for a long- time comprised all the mosqui- toes. But other genera have been erected, and now the mosquitoes are included in a family known as the Cu- licidae, which comprises several genera and very many species. Culex, however, is the typical genus, and in- cludes the commoner, most abundant, and most wide- spread kinds of mosquitoes. AVe have at least twelve species in the United States, and probably more than two hundred species exist in different parts of the world. The genus has no geographic limitation, and its species are found in the Arctic regions as well as in the tropics. Not only has the genus itself apparently no territorial re- strictions, but the individual species are many of them wides^Dread. There are a half dozen or more which may be found practically everywhere in the United States. There are others which extend from Cuba to Alaska. A few others are more restricted. The life history of the common Euro])ean Culex, known as Cnlex j^qy'iens, was studic'd and described very accurately as long ago as 1691, by Bonanni, in his " Micrographia Curiosa," i)ul)lished at Rome that year, and I am not sure that mosquito biology 66 THE COMMON MOSQUITO 67 was not well kiiowu at an even earlier date. The French observer, Reaumur, studied the same species more than 150 years ago, near Paris, and his account of the devel- opment of Culex has remained standard from that time almost to the present day. The full life history of no American species of Culex, however, was published until 1896, when the life history of Oulex jnimjais Wiedemann was worked out by the writer at Washington and pub- lished in Bulletin 4, n. s., of the Division of Entomology, of the United States Department of Agriculture. Fig. 6. — Egg Mass of Culex pungens ; enlarged; with iudividual eggs, still more enlarged, at left. (Author's illustration.) Culex jnmgens is one of our common North American si)ecies. It abounds everywhere, from the White Moun- tains of New Hampshire down into Central America, and is, perhaps, the most abundant of our mosquitoes. It breeds exclusively in fresh water, and its larvffi may every w^here be found in water buckets and barrels, in transient pools of rain-Avater, in fresh-water swamps, along the borders of inland lakes and ponds, and, in fact, in all of the out of the way places which have been mentioned in Chapter I. Its life history may be taken as typical of the genus Culex, all other species jprobably closely re- 68 MOSQUITOES senibling- this form in all of tlieir early stages aud in their periods of developnieut. The female lays her eggs upon the surface of the water, balancing herself upon some floating objs'ct during the operation, and extruding them in an irregular, raft-shaped mass, which is usually sha[)ed something like a pointed ellipse somewhat convex below and concave above, all of the eggs standing on end and closely applied, side by side, in from six to thirteen longitudinal rows, with from three or four to forty eggs in a row. The number of eggs in each batch varies from 200 to 400. As seen from above, the G^g mass is gray-brown, from below, silvery-Avhite, the latter appearance being due to a tilni of air which protects them from the water. It seems impossible to wet these es::g masses. They may be pushed under the water, but bob up apparently as dry as ever. As the eggs are very small, being only 0.7 mm. long, aud 0.16 mm. in diameter at the base, the entire e^g mass is not a large object, seldom, in fact, reaching a length of more than a quarter of an inch. The mass separates rather regularly and the eggs are not stuck together ver}' firmly. After they have hatched, the mass will disintegrate in a few days, even in perfectly still water. The individual eggs are slender, broader and blunt at the bottom, and somewhat pointed at the tip. The tip is always dark grayish-brown in color, while the rest of the Qg^ is dirty white. Sixteen or more hours after laying, the eggs hatch, generally about noon on warm days, but some- times they will remain unhatched for two days or even longer, especially in cold weather. THE COMMON MOSQUITO 69 The larvfe issue from the under side of the egg masses and are extremely active at birth, wriggling rapidly in the water about the eggs. They are very minute and move so rapidly that it is difficult to form any impression of their shape and structure except when they are at rest. Fig. 7. — Young Larvaj of Culex pungens ; enlarged. tration.) (Author's illus- They come frequently to the surface to breathe, and dur- ing the first few hours many of them remain under the e^cr mass, where they get air from the air film by which the egg mass is surrounded. One of the first peculiarities which strikes one on observing these newly hatched larvjB or wrigglers under the lens is that the mouth is furnished with tufts of filaments which are constantly in vibration. The head is large, the antennae long, the thorax somewhat swollen, and the abdomen slender. The sides of the body are furnished with stiff bristles. From the next to the last segment of the abdomen there protrudes 70 MOSQUITOES a lons" tube nearly as thick as the body itself, and it is this tube which is extruded from the surface of the water every time the larva rises to breathe. The object of this extrusion is to get air, and this tube is the l)rcathing tube of the insect. Its extremity is furnished with a breathing Fio. 8. — Mouth-parts of Larva of Cnle.r pungens ; greatly enlarged. (Autlior's illustration.) hole, or spiracle, and into it run two main trachea^ or breathing tubes, which extend through the body of the insect, giving off branches here and there, and thus carrj'-- ing air to all of its tissues. The true end of the body is furnished with four flat flaps, the exact purpose of which THE C03I3ION MOSQUITO 71 is uot known, but which may possibly function as gills while the larvse are very young, and are certainly of use as swimming organs. When the breathing tube is at the surface of the water the body of the wriggler ex- tends down below the sur- face at more or less of an angle with the water sur- face, and its mouth-parts, as just stated, are constant- ly in vibration, bringing into its mouth any minute particles which float in sus- pension in the water. Oc- casionally it descends to the bottom, jerking its body violently from one side to the other. The flaps at the end of the body undoubt- edly assist in this motion. The jerking motions are not so evident when the larva or wriggler is de- scending as when it be- comes necessary for it to ascend once more ; in other words, its specific gravity seems to be greater than that of the Avater and sometimes it can be seen to descend without effort, simply sinking Fig. 9. — Full-grown Larva of Culex pungens ; enlarged. (Author's il- lustration.) 72 MOSQUITOES down. After one of them has -wriji^prled up to the surface of the water, its breathing- tube extrudes, fresh air runs into its trachese, and the tension of the so-called surface film of the water assists it in maintaining- its position. After an introductory wrig- gle, which pulls the breath- ing tube below, the insect sinks. The larval Culex ap- pears to pass through three different stages of growth, reaches maturity, and trans- forms to pupa, in a minimum of about s(>ven days in warm summer weather. The pupa differs markedly from the larva in the great swelling of the thoracic seg- ments, as shown in the ac- companying' cwi. The pupa seems to be all head and thorax, with a slender abdo- men and with two large flaps at the end of the abdomen, which assist it in SAvimming whenever it feels that it has to sAvim. In this stag-e the Fio. 10.— Pupa of Cfilfx pun- insect is lighter than water. gens; enlarged, with Anal Seg- It remains motionless at the meiif bcldw, .still more enlarged. (Autlior's illustration.) surface and when disturbed THE COMMON MOSQUITO 73 does not sink without effort, as does the larva, but is only able to descend by violent muscular action. It wriggles and swims as actively as does the larva and soon reaches the bottom of the water. As soon as it ceases to exert itself, however, it floats gradually up to the surface once more. As pointed out in our con- sideration of the habits of mosquitoes in general, this activity on the part of the pupa is necessary to preserve it from fishes and from its natural enemies. It is very active and difficult to capture. The mortality of the pupae, however, is not great, except through the efforts of fish and its other enemies, while that of the wrigglers or larvfe is apt to be great through drowning. When- ever a larva becomes sick or weak, or for any reason un- able to exert sufficient muscular force to wriggle to the surface at frequent intervals, it drowns. It seems almost like a contradiction in terms to speak of an aquatic insect as drowning, but this is a frequent cause of mortality among mosquitoes. This fact also explains the efficacy of the remedial treatment which causes the surface of the water to become covered with a film of oil of any kind. Aside from the actual insecticidal effect of the oil, the larvae drown from not l)eing able to reach the air. Or they may draw drops of oil into the tracheae, clogging them and preventing the passage of the air. The struct- ure of the larvae and pupae at the different stages is so well shown in the accompanying figures as to render it unnecessary to describe them fully. One peculiar struct- ure of the pupa, however, has already been pointed out in the general consideration of mosquitoes, and that is the 74 31 OS QUI TOES trumpot-sliapcd broatliiiif^ org-ans, which now issnc from the thorax and no longer from the abdomen as with the larva. In Oulex pungens, these ear-shaped, trumpet-like Fifi. 11. — Adult male of Cnkx pungens; with parts enlarged. (Author's illustration.) breathing: org-ans are rather slender and of the projior- tions indicated in the fig-ure. The duration of the pupal staq-e in midsummer with this species at Washing-ton is about two daj'S. A mini- mum generation, therefore, of Culcv punr/cns will occupy ten days, as follows : sixteen to twenty-four hours for the egg- ; seven days for the larva, and two days for the pujja. THE COMMON 3f OS QUITO 75 In my observations on this species I was interested to notice that on the first day the adults which emerged from the pupse were invariably males ; on the second day Fig. 12. — Adult female of Cvle.v pungens; enlarged. (Original.) the s'l'eat majority were males, but there were also a few females ; the preponderance of males continued to hold for three days ; later the females were in the majority. The duration of a g-eneration as indicated above, is, as we have seen, a minimum duration. If a spell of cold weather should come in the middle of the summer, the 76 3I0SQUIT0ES life of the wri^-g-lers may be almost indefinitely pro- long-ed. I have watched them for twenty days, during which time they did not reach full g-rowth. The short- ness of the minimum generation, however, is ver}' signifi- cant and accounts for the fact that swarms of mosquitoes develop upon occasion in surface pools of rain-water, which may dry up entirely in the course of two weeks or less, or in a chance bucket of water left undisturbed for that length of time. Dr. John B. Smith has reared the species, as elsewhere stated, from larvae found in January frozen in ice. In studying the larv;ie after they had been thawed out he found that they remained under the water for a long time, certainly fifteen minutes, and probably much longer. These observations thus difier radically from those which I made in summer, and show that these larv;© must be studied still more before we know all that may be found out about them. This species, Cuhx pxnr/efts, is said by Dr. H. A. Yea- zie, of N(nv Orleans, to breed most extensively in the gutters in that city. They are found in gutters in whicli the water runs slowly, l)ut more plentifully' in those where there is no current. In gutters that receive the refuse of the gas works, tar factories, soap works, and oil establish- ments, there are no larvfe. They live in gutters contain- ing Mississippi River water, but do not i>rosper. Dr. Yeazie thinks the fine sedinuMit in the ^Mississippi water blocks their br(\atliinq' tub >s, since they fionrish well in this water after it hns \)vo]\ filt('r(Ml. Reverting once more to the distribution of thedifterent THE COMMON 3I0SQUIT0 77 species of Culex, I liave been able to deterniine, by exaiu- iuatiou of the locality labels in the collection of the United States National Museum, that in almost every locality in the United States there may be found five or six species of this genus. The commoner forms are Oulex conso- (//'inns, C sthiiulans, C pt'i'turhans, C. pungens, and C. im- plfjcr, and these forms are found almost all over the country, from New England to Texas, and even to southern California. C vonsuhrlmis is perhaps a more northern form than the others, and is one of the species which occurs in Alaska. It is also found in the White Mountains in New Hampshire and in the Catskill Moun- tains in New York, and occurs on the Saskatchewan River in British America, and in Minnesota and North Dakota. We have in this country no species of the genus Culex which inhabits really salt water and, in fact, no species of mosquito can definitely be said to occur in water as salt as the ocean. Three or four Australian species are said to live in salt water, but, so far as I have been able to learn, there is not sufficient substantiality in this record. Culex salinus of Europe is also said to breed in salt water. We have in the United States, however, a species of Culex which occurs in brackish water, that is to say, it is able to breed in, and prefers apparently to breed in, the brackish swamps which are occasionally overflowed at very high tides, though not affected by the daily high tide. This is Culex sollidtaiis (see Fig. 1), a small gray mosquito which has its legs banded with black and white. It is ordinarily known as the ring-legged mos- quito and is the most common form on the Atlantic sea- 78 MOSQUITOES coast. It occurs along- tho Now Jersey coast, the Long Island coast, along Staten Island, at Virginia summer resorts, and at Tybee Island, Ga., and Ht. Augustine and Charlotte Harbor, Fla. Curiously enougli, Dr. A. D. Hopkins states that what is probably this same species apparently breeds in AVest Virginia in pools and small streams fed from coal-mine drainage, the water of which contains a large jiercentage of sulphate of iron. There is no doubt that this Culex breeds in great num- bers in the pools left by the highest tides, which subse- quently become freshened to some extent by rains or by the entrance of spring water. It has been caught, how- ever, considerable distances inland, and the question arises, has it been carried to such spots by trains only, or will it breed after being so carried for at least one or two generations in fresh water? Mr. Benjamin S. Pas- chall, of Newfield, N. J., caught this species in August, 1900, in his garden. They could be found anywhere in the long grass, practically by the thousands. Newfield has one of the highest altitudes in South Jersey, being about 130 feet above the tide and over thirty miles from the sea. In Mr. Paschall's opinion, the si)ecies must breed there. There had been no wind for a long time before their appearance and the microscope showed all specimens to be freshly hatched. On Seiitember •4th, he tried an experiment and placed a pail of water in a spot where these insects were thickest. By the end of a week he had procured many eggs, and September 14th he succeeded in hatching out several hundred mosquitoes, but not one single specimen of noUicitans; all were ^>?//j- THE COMMON 31 OS QUITO 79 gens. He concludes that CuJex soUicitans appears in the perfect state throughout South Jersey, being- found from May to October, but is not always common. Mr. La Rue Holmes, of Summit, N. J., has several times sent me specimens of sollicUans taken at Summit, which is about twelve or fifteen miles from the nearest salt marsh. I am inclined to think that although this species may be found widespread through the summer in various jjarts of New Jersey, this abundance is due to its car- nage in numbers from the sea-coast by railway trains, and even if it does breed for a generation or two in fresh water, the supply is constantly renewed from the sea-shore. Culex impiger is another of the more northern mos- quitoes, having been collected by Mr. Trevor Kincaid on the Harriman Alaskan Expedition, and having been g-iven me by Dr. Walter Evans, of the United States Department of Agriculture, who has investigated the agricultural re- sources of Alaska. Mr. F. C. Pratt has found it breeding in privy vaults in Alexandria, Va., and this species is likely to be the one found usually in such places, where the water is fouled with decomposing- or excreted animal matter. The distribution of our commoner species of Culex, so far as known to the writer, is as follows : Culex consobrinus Desv. Habitat : White Mountains, N.H. ; Beverley, Mass., Septem- ber 28 (Nat. Mus.) ; Catskill Mountains, Greene County, N.Y., 2,500 feet (Howard); Hlinois, March 21, April 29, May 6, October IG (Nason); St. Anthony Park, Minn. , April, so 310SQU1T0ES May, oil snow (Lugger) ; S;i.skatrlif\v;iii River, British America; South Dakota (Nat. JMus. ); Lincohi, JSeb. May, September (Bruuer) ; Colorado (Nat. Mus.j ; Hot Springs, Ark. (Curry); Los Angeles, Cal., February (Co- quillett) ; Argus Mountains, Cal., April (Nat. Mus.) ; Santa F6, N. Mex., July (Cockerell) ; New Orleans, La., Novem- ber (Thayer) ; Ottawa, Canada, May (Howard) ; Summit, N. J. (Holme.s) ; Trenton, Ontario, May 34 ( Fletclier) ; Flat River, Mo., Kovx'mber (Pergande). CULEX ANNULATUS Meig. Habitat : New Bedford, Mass. (Johnson) ; Lincoln, Neb., May (Bruner) ; Santa Fe, N. Mex., July (Cockerell) ; Stan- ford, Cal. (Kellogg) ; Laggan, British Columbia (Wick- ham). CULEX IMPIGER Walk. Habitat : White Mountains, N. H. ; Beverley, Mtiss., May 24, June 2 (Nat. Mus.) ; Ithaca, N.Y., July 9 and 17, August 28 ; Wiliuuth, N.Y., June 10 (Comstock) ; Saskatchewan River, British America (Nat. Mus.) ; Miunesotii (Lugger) ; Loudoun County, Va., August 20 (Pratt) ; Tyrone, Ky., July 14 (Garman) ; Georgia (Nat. Mus.) ; Mesilla, N. Mex. (Cockerell) ; Lsle of IMiies, West Indies (Scudder) ; Port- land, Jamaica (Johnson) ; District of Columbia, Septemljer 12 (Barber); Alexandria, Va. (Pratt) ; Ogdensburg, N.Y., June 3 (Howard) ; Bulfalo. N.Y. (Wright) ; Middletown, Conn., June (Davis) ; Ottawa, ('anada, May ;jl (Howard); Chats Rapids, Quebec, May 24 (Fletcher) ; Buckeye, Wash. (Nat. Mus.) ; Stikine River, British Columbia (Wickham) ; City of Mexico (Herrera). CULEX PKRTUHBAX.S Walk. Hal)itat : Lakeland, Md., August s (Pratt) ; Virginia, August 17 (Pergande); Tick Island, Fla., May 12 (Johnson); THE COMMON 310SQULT0 81 Texas (Nat. Mus.) ; Bayaiuon, Porto Rico, January (Busck) ; District of Columbia, September 1-5 (Barber) ; St. Elmo, Va., June, July, V^irginia Beach, August (PrattJ ; Mel- bourne, Fla. (Peek); Cuba (Lazear, Read). CULEX PUNGENS Wied. Habitat : Ottawa, Canada (Fletcher) ; White Mountains, N.H. ; Beverley, Mass., September 5 ; Cambridge, Mass., September 16 to November 5 ; Boston, Mass. ; Baltimore, Md., November 5 (Nat. Mus.), November 26 (Lugger); Charlton Heights, December 1 (Pratt) ; District of Colum- bia, January 30, March 5, May 6 and 15, June 28, July 11, August, October 10, 15, 25 and 31, November 4, 8, 13, 16 and 23, December 23 (Pergande) ; Ithaca, N. Y., May 29. July 17, August 28 (Comstock) ; Illinois (Nason) ; Minne- sota (Lugger) ; Lincoln, Neb., September 20 (Bruner) ; Lexington, Ky., November 10 (Grarman) ; New Orleans, La., December 17 (Howard); San Antonio, Tex., May 5 (Marlatt) ; Hot Springs, Ark. (Curry) ; Georgia, August (Coquillett) ; Melbourne, Fla. (Peek) ; Portland, Jamaica (Johnson) ; Mexico City (Barrett) ; District of Columbia, August 22, 28, September 1 (Barber) ; Jackson, Va., October (Thayer) ; Woodstock, Va., June (Pratt) ; Newport News, Va., October (Thayer); Stillwater, Okla., June (Bogue) ; Philadelphia, Pa. (Woldert) ; New Orleans, La., June (Veazie) ; Eastern Texas (Woldert) ; Summit, N. J., May (La Rue Holmes) ; Newfield, N. J. (Paschall) ; Middletown, Conn., June (Davis) ; Cuba (Lazear, Reed) ; Agric. College, Miss. (Herrick) ; Flat River, Mo., November (Pergande), Bluefields, Nicaragua (Wailes) ; Gruanajuata, Mex. (Duges). CULEX STIMULANS Walk. Habitat : White Mountains, N. H. ; Beverley, Mass., June 2, July 9 ; Cambridge, Mass., May ; Jamaica Plain, Mass., 82 MOSQUITOES August 25 (Nat. IMus.) ; Siasconsett, IMass. (Wilder) ; Bal- timore, Md. (Lugger) ; Illinois, August 1, iSei)teiuber 15, October 5 (Nasoii) ; Agricultural College, Mich. (Gillette) ; Saskatchewan River, British America (Nat. Mus.) ; Lin- coln, Neb. (Bruner) ; Colorado (Nat. Mus.) ; Ithaca, N. Y., June 13, 18, 2!), July 14, August 28 ; Wilniuth, N. Y., June 10 (Comstock) ; liochester, N. Y. (Ewers) ; BuUalo, N. Y. (Wright) ; Brooklyn, N. Y. (Van Matie) ; Georgia (Nat. Mus.); Bladensburg, Md., May 27 (Barber); St. Elmo, Va., June 5 (Pratt) ; District of Columbia, Septem- ber (Barber) ; June 10 (Miss L. Sullivan) ; Ottawa, Canada, June 1 (Howard) ; Ogdensburg. N. Y. , June 3 (Howard) ; Rochester, N. Y., June (Ewers) ; Sumnnt, N. J., May (La Rue Holmes); Middletown, Conn., June (Davis); Lake Maxinkuckee, Ind. (Evermann) ; Mesilla, N. Mex., Octo- ber 20 (Cockerell) ; Tacna, Ariz., April 13 (Hubbard) ; Jua- rez, Mexico, May 12 (Cockerell) ; Summit, N. J. (Holmes) ; Flat River, Mo., November 1 (Pergaude). CULEX SOLLICITANS Walk. Habitat : Maine, August ; Beverley, Mass., June, September 15 (Nat. Mus.) ; Siasconsett, Mass. (Wilder) ; Avalon, An- glesea, and Atlantic City, N. J., July 10 to 29 (Johnson) ; Summit, N. J., September (Holmes) ; Far Rockaway, Long Island, N. Y. , August 30 (Howard) ; District of Columbia (Pergande) ; Georgia (Nat. Mus.) ; St. Augustine and Char- lotte Harbor, Fla. , July; Portland, Jamaica (Johnson) ; Chesapeake Beach, Md. (Barber) ; Baltimore, Md. (Thayer); Plymouth, N. C. (Thayer). CULKX TAU.'^ALIS Coq. Habitat : Argus Mountain, Cal. , April ; Folsom, Cal., July 3 (Nat. Mus., Koebele) ; Stanford, Cal. (Kellogg) ; Corval- lis, Oregon (McElfresh). THE 003131 ON 31 OS QUI TO 83 CuLEX TRiSBRiATUS Say. Habitat : White Mountains, N. H. (Nat. Mus.) ; Delaware County, Pa., June 12 (Johnson) ; Washington, D. C, May 5 and June 10 ; Loudon County, Va. (Pratt) ; Near Balti- more, Md. (Thayer) ; Roanoke, Va., October (Thayer) ; Middletown, Conn., June (Davis) ; New Jersey (Woldert). Dr. J, B. Smith's Observations on Culex 2ningens. The observations made by the well-kuowu State ento- mologist of New Jersey ou the hxrvje hibernation of Cidex piDigens in pitcher phints are of such great interest that they are given in full from advance sheets of an article which Dr. Smith has been good enough to send me and which was prepared for the Entomological News. New Jersey's reputation for mosquitoes is well established, and more people come into our State annually to be bitten by our shore species than go to any other State in the Union for any like purpose. In some of the swampy districts in the Pines they make life a burden at times, so when my good friend, J. Turner Brakeley, wrote me in the late summer that in looking at the contents of some pitcher-plant leaves he had found mosquito larvcS in abundance in the water they contained, it made no especial impression upon me. It was in a way what I would have expected, though no one had noted this so far as I could then remember. Dr. Riley at one time bred a number of species from this plant ; but seems either to have found no mosquitoes or to have ignored them. Mrs. Treat made many interesting observations on the feeding habits of the plant itself, feeding the leaves with raw meat in place of the insects that ordinarily fall into them : but she also ignored the mosquitoes. 84 N()S(jri7'()/'JS Luto in November (t!»(K)), I spent three clays with Mr. lirukejey at Ijahaway aiul one of our walivs \v;is into a hucklel)erry and wild eranberry swani[), where pitclicr plants were al)undant. Tliough the weather was yet mi hi, inoscjuitoes were no ionj^er obtrusive. There were oeeasional specimens, to l)e sure, l)ut tliey seemed to be left-overs not yet in iiibernatinf;- (piarters. The interesting point was that in every leaf examined there were wri}::glers, varyinjj^ in size from an eightli to a (piai-ter of an ineh in lengtli. Tliere was always a mass of insect fraguients at the bottom, say from one half to an inch in depth, and in composi- tion this varied from a dense black ooze at the lowest point to entirely or only i^artly decayed specimens at the top of the mass. The question arose at once whether these larv;e would yet develop that season, and from pul)lished accounts I assumed that they nuist, or perish. J)r. Howard, in his careful account of the species of Cule.x, and es[)ecially C. puil(/eiis, says nothing of larval liil)ernation. He records finding adults and, indeed, this was in accordance with my own experience. The nuitter dropped here until late in January when, during a bitter cold spell, Mr. Hrakeley cut out a few i)itcher leaves, stripped them from the core of solid ice they contained, and looking through it saw wrigglers imbedded in all parts of it, in all .sorts of shapes; but mostly in a half coil. The temperature of the bog had been down to 2° below zero, as registered by a standard minimum thermometer, and radiation probjibly lowered this even more. A number of leaves were gathered, the cores of ice with all they contained were removed, and the lum|)s were placed together in a jar in a moderately warm room. The ice melted slowly, and as the larva' were gradually freed, they droppi'd to the i)()ttom, Avhere for a time they rested, apparently lii'eless. Hut as the amount of ice decreased, feeble motions here and tlu-re indicated a revival, and long before the lumps were completely jnelted. THE COMMON MOSQUITO 85 those first released were moving about actively. This, be it noted, was in water not much above the freezhig point. Soon after the ice had melted and the debi-is had settled, the insects were busily engaged in apparent feeding. The specimens were sent to me as a curiosity, January 22d, and arrived in very good condition. A few had succumbed to the dangers of the journey, but altogether there was a good lot of lively wrigglers. The bottle was nearly full of water, it had had a five mile wagon drive over a rough road, had been trans- shipped no less than four times before it reached New Brunswick and was thrown into the delivery wagon. Under these circum- stances any regular I)reathing of the kind usually described was utterly out of the question, and drownings should have been numerous ; but really only a very small number of specimens died. At short intervals other jars were received, all of melted ice taken from pitcher plants, until I had several hundred active wrigglers in eight different jars. 8ome of the leaf chunks, Mr. Brakeley informs me, had only a very few larvae — ten or a dozen; ■ others ran as high as thirty or more. The jars were all placed on a counter shelf near a steam radia- tor and it was expected that in a few days there would be pupae and adults. But the days passed into weeks and the weeks into months, without change other than a gradual — a very gradual, increase in size. The larvae were just as active and lively as they could be expected to be, and were feeding continuously; but evidently something was lacking. Besides, they did not in all respects behave as, according to Dr. Howard's account, they should have done. I do not suggest that the account as printed is not a perfectly accurate record of facts: merely that my speci- mens were Jersey mosquitoes and therefore a law unto them- selves. As the fragments settled to the bottom, the water became 86 MOSQUITOES almost entirely clear ami larvae congregated over this sediment, feeding head down and frequently rooting into it; varying the process by working along the glass of the jar on the side away from the light. It was very rare that an individual was observed at the surface with the spiracle in breathing position. I watched patiently several times, for fifteen minutes at a time, without noting a single individual rising to the top. Mr. Dick- erson, one of the students, watched more or less continuously for two hours on one day and declares positively that during that period only a small percentage of the entire number came to the top. On two or three occasions where my work was such as to allow it, I kept a jar within sight the entire day, and I have no hesitation in saying that some individuals remained below the surface for hours. Occasionally a number of specimens would be at the surface, feeding, head up, so that the mouth-brushes skimmed the sur- ffice, and these were watched on occasions for fully twenty minutes without noting any attempt to assume the breathing position. In fact, during the two months that these larvje were under daily observation, the rising to the surface to breathe was the rare exception rather than the rule. As to feeding positions, all of those figured by Dr. Howard Avere noted. Usually they were head down, over the bottom sediment, or head up, feeding along the sides of the glass or at the top. The mouth-brushes serve as organs of locomotion as well as for feeding, and the insects are perfectly al>le to make their w.ay from place to place without moving any other part of the body. The jerky, wriggling motion is used when they wish to get away quickly, and as often to get down to the bottom as to get up to the surface. They can, and often do, sink slowly to the bottom without any motion whatever, and oft<'n, to sink more r.tpidly, tiiey curl theniselvcs up into a ring. ( )c('asion;illy a speci- THE COMMON MOSQUITO 87 men will get hold of a bubble of gas forming at the bottom, and will allow itself to be floated to the surface. It is immensely inter- esting to watch these little creatures ; but as week after week went by without change it became just a little tedious. To has- ten matters a little, on March 1st I placed the two jars first re- ceived on a water bath, which was kept at a temperatui'e as nearly constant as the varying gas pressure allowed. Ordinarily the thermometer ranged between 100° and 110°, but it has gotten as high as 120° and as low as 90°. These were exceptions, however, and not exceeding the ordinary out-door range in June. The temperature of the water in the jars ranged between 80° and 90° almost uniformly. A difference in the rate of growth was observable after a few days, and several specimens seemed approaching the adult con- dition ; finally, on March 18th, I noticed the first pupa, seven- teen days after placing the jar on the water bath. From this the adult emerged March 31st and proved to be a female Culex pungens. Three other pupse were formed within a Aveek after the first, and a second adult, also a female, was obtained March 24th. As to the habits of the larv» in the two jars artificially forced there was little to note as different from those in the normal laboratory temperature, which varied from 40" to 78°, averaging a little under 70° for the twenty-four hours. They fed in much the same manner, kept away from the light as much as possible, passed most of their time at the bottom, but were more lively and more frequently at the surface. The jars were kept covered except for a few minutes each day and in none of them did the water foul, despite the vegetable and animal matter present in each. On March 24th I made an experiment that resulted fatally. It occurred to me that possibly the slow growth was due to lack of food, and Mr. Brakeley had written me that the wrigglers at- tacked and devoured a small gnat which Avas breeding in his jars, 88 MOSQUITOES suggesting that possibly a mutton chop might help matters along. On March 24th, I put a small lump of raw Ijeef chopped fine, into eacli of live experiment jars. The next day I could give only a casual glance before going out of town, and thi.s showed noth- ing unusual ; but the day after, March 2()th, when I reached the lai)oratory at 8 A.M. I saw at once that something was wrong, lie- cause all the living larva- were at tlie surface, lie.ul down, s])ira- cles reaching the air. In every jar into which 1 had jilaced the meat I noted the same apiiearance, and 1 hastily fished out every particle. But it was too late : more than half were alreatly dead, others seemed to show fungoid growth proceeding from the seg- ments, so, to prevent their dying, I killed them off with a dose of formalin. One large jar received in Fel)ruary was left unharmed, and this was placed on the water-bath Marcli 2Gth. Nothing has come from it at the date of present writing, and nothing may ever come from it, but its history must be written later. But this experiment, fatal as it proved, was of some value. It shows that water too foul with animal decay is not suitable for mosquito larv;p.* Vegetable decay and the harder refuse from insect Ixxhes will help along the development ; but beyond that the water must be clean. It seems to indicate further that the conditi(»n of the water may very largely determine the frequency with which the supply of oxygen nnist I )e renewed from above the surface. In June, with a supply of water at a relatively high temperature in which microscopic life is swarming, I have no doubt Dr. Howard's observations would i)e exactly dtq)licated. With the same species in clear water, at relatively low tempera- ture, the breathing habits are quite d liferent and the insects ob- tain, I have no doubt, a goodly portion of their oxygen from the * This generalization is nuicli (oo bread. The larva' of Culcr impiger, for example, will swarm in water foul wilii decomposing animal matter, and so, possibly, will larvfp of certain other species of Culcx.— !>. O. 11. THE COMMON 310SQUIT0 89 water itself. Just how they do this I am not prepared to say. One tiling may be considered as certainly established by this series of observations : the insect can and does hibernate in the larval stage, if this is not, indeed, the prevailing method. Mr. Brakeley has scoured the swamps for miles about within the last few weeks, and wherever he found pitcher plants almost or quite every leaf had its supply of wrigglers. It is not, therefore, a local phenomenon. Nor is it even suggested that pitcher plants alone furnish breeding-ijlaces where the larv* hibernate ; but they are remarkably safe resorts, protected to a very marked extent from natural enemies. Is there any relation between plant and insect, whereby the plant receives a benefit? Do the wrigglers in any way prevent a foulness of the water from the insect fragments until the plant has absorbed what it needs? It is noticeable that during the whole winter only a single ex- ample of Culex pungens was taken in the barns, storehouses, or cranberry-sorting rooms, though they were diligently sought. AnopheleH punotipennifi were found quite abundantly— between twenty and thirty specimens having been taken on the windows of the sorting rooms ; but no Anopheles larvae were found in any of the collected leaves. As a. Jerseyman, Mr. Brakeley oi-dinarily pays little attention to mosquitoes, but he could not easily over- look Anopheles, did it occur in any numbers in sunmier. He says that it does not, and that he has never seen as many during his years of residence in the Pines as he did this past winter. My own experience is similar. I remember that about three years ago I was annoyed by Anopheles very early in the year in my store-room in the basement of the Station Building. Later on I saw nothing of them, and I can say positively that the spe- cies of this genus form no i^art of the often considerable swarms in and near New Brunswick. In the cellar of my residence I took Culex pungens, female, March 22d, flying. It could not well have developed there, and 90 MOSQUITOES of course there c£Ui be no doubt that the species hibernates as an adult as well as in the larval stage. These pitcher-plant leaves contain, besides mosquito larvje of this species, considerable numbers of other larvue, -which Mr. Brakeley succeeded in breeding. Some examples submitted to Mr. C. W. Johnson he pronounced to be Aedes f uncus O. 8., a s[)ecies by no means commonly observed. The present series of notes are not by any me.ans a complete rec- ord of the observations made on the wriggler colonies at New Jirunswick and in the Pines, and they are not even ended ; but they will serve to call attention to one or two heretofore unob- served facts. They also contain a suggestion. Is it not prob- able that the mosquitoes that swarm in Alaska and in arctic regions may pass the winter in the larval stage, frozen in the solid ice, ready, when the melting time comes, to mature rapidly? Hiding-places for adults are occasionally somewhat scant in such regions, and the swarms are said to be even more numerous and vicious than they are in New Jersey. [Note.— Since this matter was put in type, Dr. Smith writes me that from recent roarings lie is led to believe that most of his statements, especially with regard to llio ability of larvse to remain under water a long time, lefer to Acdes and not to Culex. — L. O. 11.] IV The Malarial Mosquitoes of the Genus Anopheles TO physicians and others who are investigating the malarial conditions of a given neighborhood it becomes very important to know everything con- nected with this most noxious genus of insects. Not only is it necessary to be able to recognize them in every stage of their existence, but also to know the character of the pools in which they will be found in their early stages, since much time may be wasted in searching for them in places where they could not possibly occur, or in which they are not likely to be found. This point must be borne in mind, therefore, by those who, looking through this chapter, think that the writer has gone into the subject with apparently unnecessary detail. The genus Anopheles was founded by Meigen in 1818. The first reference to its early stages which is to be found in literature is in a f)aper entitled " Description of a New Fish which I found in the water of the basin of S. Mag- loire of the Fauxbourg S. Jaques at Paris, which can be called an Aquatic Caterpillar," published in Paris in 1754 by an observer who possessed the euphonious name of 91 92 MOSQUITOES Joblot. He fioun'S tho larva, which is recognizable as that of Auoi>heles. The Dutch observer, Meinert, gave the next accurate (lescii])ti()n and figure of the larva in 188(), and other descriptions and tigures were puljlished l)y tlu! Italian, Ficall)!, in l(Si)i), and the Englishman, Giles, in 1900. Tlu! various stages of one of these species were described and figured in 1900 by the Italian, Grassi, and by the present writer. At the time I published these ob- servations, I supposed that I was the first person in Amer- ica to have seen Anopheles larvae, but Dr. Charles Sedg- wick Minot, of the Harvard Medical College, wrote me, after seeing- the first edition of Ihdlctin 25, that he raised Anopheles twenty-five years or more ago without suspect- ing- its id(Mitity. At that time Dr. INIinotwas much in- terested in eutomolog-y. He has since hunted up his old notes, and has published an account of his early observa- tions in the journal of the Boston Society of Medical Sciences, vol. v., January, 1901. Th(^ specic^s which I studied in full in the siimmer of 1900, and which was treated in my liulletin 25 as Ano])he- les (jiKiilr'niKiciilatiis Say, has been definitely decided to be identical with the AaopJieles hidct/h'/x'/uiis of Europe.* * Osteii 8;ickci), KiilomologidH Mimtlih/ Mi)iis ^l. is not unconnnon in the Mark Branden- burg, in localities where water is abundant ; for instance, it is (juite THE MALARIAL 3I0SQUIT0ES 93 Dr. W. S. Thayer saw the European species in Grassi's laboratory in Italy, and on liis return to this country told me that he thought the two forms were identical ; and the English student, F. V. Theobald, who is monograph- ing the mosquitoes of the Old World for the British Mu- seum, has studied a large series of specimens from this country and has decided that the European and American forms are identical. This at once suggests the interesting question as to whether this abominable creature was in- troduced from Europe to America or the reverse. It is quite within the bounds of possibility that malaria was originally an European disease and that not only was the disease itself carried from there on sailing vessels, but the mosquitoes which propagate it as well, at least to America. The Life History of Anopheles rnacuUpennis. The Adult. — The accompanying illustration (Fig. 15) will show very well the general appearance of the adult insect. It is a rather large mosquito and is very bloodthirsty. It is attracted to the house in numbers. The differences between the males and females are well brought out in Fig. 15, and the striking feathery antennae and palpi of the male render it very conspic- uous. The wing markings and the color of the palpi differentiate this species from our other species of common about Fiieiiwalde in niiilsumnier. Its sting is more painful tlian that of any gnat I know, and lias a nincli more pernicious elTcct. During a l)otanicai excursion of several days which I made with some of my ]iupils, I noticed that the sting prodnced deep purulent wounds, whicii it took several weeks of careful medical treatment to heal." 94 MOSQUITOES Anopheles, and the long palpi of the female at once distiug-uish it from all species of Ciilcx. Resting- Position. — Owing to the publication of a field sketch made at Sierra Leone by a member of the Ross ex- pedition, the writer has been much interested in watch- ing the resting positions of the adult insects. He finds that when resting upon a horizontal surface — such as the ceiling of a room or the covering of breeding-jars — the insect clings with its four anterior legs in a nearly per- pendicular position, its beak thrust forward toward the surface to which it clings. The hind legs are frequentl}'^ in motion, but as a rule hang downward with more or less of a bend at the knee joint (femoro-tibial articulation). When resting upon a perpendicular surface, however — such as the side wall of a room or the side of a breeding- jar — the body is held only at a comparatively slight angle from the surface. Sometimes it is nearly parallel with the surface. At other times it assumes an angle of 10° to 20° (occasionally even as great an angle as 30° to 40°), the proboscis being held nearly in line with the body. Here again the insect supports itself by the four anterior legs, the hind leg dangling down with more or less of a bend at the knee. This position is common to both males and females, and is illustrated in Fig. 13. When the body is held parallel, it will generally be found that one of the middle or hind legs has been broken off. They are very delicate and readily break. The writer has taken the liberty of having Figure 14 engraved from a drawing sent him by Mr. C O. Water- house of the British Museum. Mr. AWiterhouse made the Fig. 13. — Resting Position of Anopheles ; enlarged. (Author's illustration.) Fig. 14.— Resting Position of Anopheles above, Culex be- low ; enlarged. (From sketeh by C. O. Water- house.) 96 MOSQUITOES drawing- liimself and wrote : " Wliatevor may bo tlie attitude of Anopheles, it is all in one line. Culex is angu- lar, liunipbacked." ■ Note of Female. The peculiar hum of the mosquito is well kuown. There is a distinct diliercnce between the FiC4. 15. — Anopheles ranculipennis, tiialo ;it left, fcniale at I'iglit ; eu- laigxHl. (AuHkh'.s illustiatii)i).) hum of ^l/)nji/icles tiKtcullpciuii.s and that of the com- mon species of Culex, in that the former is noticeably lower in tone. The note of Culex as it approaches the ear is high in pitch ; that of Anopheles is certainly sev- THE 3IALABIAL MOSQUITOES 97 eral tones lower and of not so clear a character. In quality it is something- between the buzzing- of a house fly and the note of Culex. Mr. Pratt states that he can at once distinguish the two genera in this way as he is sit- ting reading in the house, and the writer feels quite sure Fig. 16. — Egg Mass of Anopheles maculipeniiis ; enlarged. (Author's illustraliuii.) after listening to them in breeding-jars that the statement is correct. These observations have been made with an abundance of material, nearly 100 adults having been under obser- vation. The Eggs. — The well-known and often-mentioned raft- shaped masses of eggs of Culex are not even remotely 98 MOSQUITOES mmm resembled by the Anopheles oviiDositions, and the indi- vidual eg-gs are equally dissimilar. In the accompany- ing- illustration (Fig. IG) the egg mass of Anopheles is illustrated for comparison with Fig. 7. In Culex from 200 to 400 egg-s are laid in a mass ordinarily shaped like a pointed ellipse, convex below and concave above, all the eggs perpendicular, and stuck closely together at the sides by some gummy secretion, and arranged in rows. The mass with Anopheles, however, is laid loosely upon the surface of the water, each cg^ lying upon its side instead of being placed upon its end as in the egg mass of Culex. They are not attached together except that they naturally float close to each other, and there are from -40 to 100 eg-gs in each lot. In CuJc.r, 2^itnr/rns the individual egg is 0.7 mm. long and O.IC mm. in diameter at the base. It is slender, broader, and blunt at the bottom, slenderer and more pointed at the tij). The tip is always dark grayish brown in color, Mdiile the rest is dirty white. The egg of Anopheles when seen from above is of rather regular el- liptical outline, the two ends having practically the same shape ; seen from this side, it is strongly convex below and nearly plane above ; seen from beloAv, it is dark in color, and when examined with a liigli power is seen to Fio. 17. — Individual Egt^s of Anopheles maculipennis, from below ul left, from above at right ; greatly enlarged. (Au- thor's illustration.) THE 3IALARIAL MOSQUITOES 99 be covered with a reticulate liexag-onal sculptiiriDg-. At the sides, iu the middle, there appears a clasping mem- brane with many strong- transverse wrinkles. Seen from above, the eg^ is black except for a clasping membrane which nearly meets on the middle line in the middle third of the body, b^^t retires to the extreme sides for the anterior and posterior thirds. At each end the color is lighter, with a group of from 5 to 7 minute dark circular spots. It is 0.57 mm. long. Eggs laid April 26tli hatched April 30th. Others laid May 13tli and 14tli hatched May 16th and 17th. The Larva. — The larva is quite as unlike that of Culex pungens as is the egg. It diflers in structure, in its food- habits, and in its customary position, so markedly, that it can at once be distinguished with the utmost ease. The larva of Culex, it will be remembered, comes to the sur- face of the water to breathe, thrusting its breathing tube through the surface layer and holding its body at an an- gle of about forty-five degrees with the surface of the water. While in this position its mouth-parts are in mo- tion and it is taking into its alimentary canal such minute particles as may be in the water at that depth, but these are naturally few in number and the larva descends at frequent intervals toward the bottom to feed. The want of oxygen, however, causes it to wriggle up again to the surface at very frequent intervals. Its specific gravity seems greater than that of water, so that it reaches the surface only by an effort, and the writer has already pointed out, in the case of Culex pungens, that when the larva becomes enfeebled and is not strong enough to 100 MOSQUITOES ^viioole up to the surface, it diowus. Feeeliug- iis it does at the bottom upon the heavier i)articles which sink, its specitic gravity is exphiiued. The hxrva of Anoiihtha maviilipeunis, however, habitually remains at the surface of the water. Its breathing tube is very much shortt'r than that of Culex, and its body is held not at an angle at the surface, but practically parallel with the surface anel immediately below the surface lilm, so that portions of its head, as well as its breathing tube, are practically out Fic. 18. — Young Larva of Anopheles maculipennis ; enlarged. (Author's illuslruUon.) of the water. Its head rotates upon its neck in a most ex- traordinary way, so that the larva can turn it completely around with the utmost ease, and feeds habitually with the under side of the head toward the surface of the water, w'hereas the upper side of the body is toward the surface. In this customary resting position the mouth parts are working violently, the long fringes of the mouth-parts causing a constant current toward the mouth of particles floating on the surface of the water in the neighborhood, which thus gradually converge to this THE MALARIAL 3I0SQUIT0ES 101 Fig. 19.— Half-grown Larva of Anopheles macnlipennis; enlarged. (Author's illus- tration.) miniature maelstrom and enter the alimentary canal. The spores of algae, bits of dust, minute sticks, bits of cast lar- val skins, everything- - in fact which floats, follow this course, and, watching- the larva un- der the microscope, they can plainly be seen to pass through the head into the thorax until they are obscured by the dark color of the insect's back. Occasionally, too large a frag- ment to be swallowed with ease clogs the mouth. Sometimes it enters the mouth and sticks. In such cases the head of the larva revolves with lightning-like rapidity and the fragment is nearly always disgorged, although some- times it is swal- lowed with an evi- dent effort. Since the Anopheles lar- va feeds only upon these light, floating particles, its spe- cific gravity is near- ly that of the water itself, and it supports this horizontal position just beneath the surface film with comparative case, and, in fact, with- out effort, the tension of the surface film itself being hardly 102 MOSQUITOES needed to liold it. It requires an effort, in fact, for the Anopheles larva to descend (which it apparently never does up to the period of the final larval staofe, except when alarmed), while it requires an efi'ort for the Culex larva to ascend. Structurally the differences between the half-grown larvpp of Culex and Anopheles- are well shown in Figs. 19, 19a, and 20. The g-roat size of the head of Culex, as con- trasted with the small head of Anopheles, is a most strik- Yi(\. 20. — Half-grown Larva of Anopheles waculipennis ; enlarged. (Author's illustration.) ing difference. The very long respiratory siphon (as Miall calls it) of Culex contrasts markedly with the short one of Anopheles. The arrangement of the hairs is entirelj' different; the branching of the hairs of Anoi)heles, as contrasted with the simple hairs of Culex and the little paired star-shaped (apparently branchial) tufts on the dorsum of Anopheles, is entirely absent with Culex. The fla]is at the tail end of the body are similar in num- ber, but are held in a somewhat different ])osition. THE MALABIAL MOSQUITOES 103 The larv?p first studied — those which hatched from the eg-gs on April 30th — grow very slowly for a number of days. This was partly owing to cool weather in the early part of May, and partly, I believe, to the absence of proper food. They were reared in glass jars of water, with sand at the bottom and a willow twig- rooting- in the sand. Fig. 21. — Full-grown Larva of Anopheles macvMpennis slinwins: head upside down, with lop of head above, at left ; greatly enlarged. (Au- thor's illustration.) As above noted, they swallowed every small particle float- iug on the surface of the water, and the dark coloration shown in Fig. 18 was largely due to the fact that most of these food particles were dark colored. About the lOtli of May, the larvae having passed through two molts, a small quantity of the green algiie growing on the lily ponds on the Department grounds was placed in the jar. The 104 3I0SQUIT0ES larvfc commenced to thrive much better, crew rapidly, and the general color of the body changed to green. The description of the habits given above held well until after the last molt preceding the change to pupre. In tliis final larval stage, as shown in Fig. 21, the diameter of the thorax became much greater in comparison with the rest Fio. 22. — Head of Larva nf Annplieles runcii/ipennis, unilcrsido; greatly enlarged. (Afler Nutlall.) of the body. The larva was less marked, more incon- spicuous, and altered its fi^eding habits to some extent. After remaining at the surface of the water, fi^eding, as before, upon floating partich^s, for some time, it would wriggle violently and descend to the bottom, where it would remain frequently as long as ten minutes before reascending to the top. Its appetite was evideutlj'^ so THE MALARIAL MOSQUITOES 105 great that it was not satisfied with the floating parti- cles, and Avhen it descended to the bottom it mouthed the particles of sand, apparently swallowing the slime on the little stones and frequently even picking up quite a large sand pebble and then dropping it again. In this stage the individual which grew most rapidly remained only four days, and transformed to pupa on the morning of the Fig. 23. — Enlarged Head of Larva oi Anopheles mnciilipennis, from side; greatly enlarged. (After Nuttull.) 17th, after a larval existence of sixteen days. The accom- panying figures of the larvae have been drawn with such care that detailed description will be unnecessary. They were drawn from life under the compound microscope. Some of the structures are puzzling, notably the organs occurring on the dorsum of the abdominal segments, shown most plainly in Fig. 20, and which look as though they might be spiracles until they are examined under a 106 MOSQUITOES liio-li power in the cast skin. The writer does not care to risk an exi)rossion of opinion as to their function, although possibly it is known, and iliey possibl}^ occur in other dip- terous hirvjp. In the early stages of the larva} they re- semble minute branchial tufts, but no tracheal connection has been found. The Pupa. — The accorapanying- figure (Fig. 24) well rep- resents the differences between the pupa of Culex and Fig. 24.— Pupa of Anopheles at riijlit ; Culex at left ; enlarged. (Autiior's illustraliori.) that of Anopheles. In this stage the insects of tlu^ two genera are not so markedly differiMit as in the larval stage. Structural differences need not W (h^scrilxMl, as they are sufficiently shown in the illustration. The eye will at once be caught by the difference in ]iosition, the pui):i of Culex resting in a more perjieiidicnlar attitude than that of Anopheles ; and the marked difference in shape between the respiratory siphons, which issue from the thorax iu- THE MALARIAL MOSQUITOES 107 stead of from the anal end of the abdomen, will at once be noticed. The pupa of Anopheles is quite as active, when disturbed, as is that of Culex. If one touches the surface of the water near it with the fing-er, the pupa at once wriggles violently away, returning shortly to the surface for air. The duration of the pupal stage in Anopheles varies according to the weather. Five days was the minimum observed during June, although several specimens re- mained in this stage for ten days. The adults issue as do those of Culex. The entire life round, therefore, of Anopheles viaculi- pcnnis in the generation studied by the writer is as follows : egg stage, three days ; larval stage, sixteen days ; pupal stage, five days ; making a total period in the early stages of twenty-four days. It should be stated, however, that during the early larval existence, toward the end of May there occurred nearly a week of cool weather, so that it is certain that in the hot season in July and August the growth and transformations will be more rapid. It will be remembered that the writer traced Culex pungens through an entire generation in the latter part of June, in ten days. European Observations on the Same Species. Nuttall and Shipley state that when the eggs are first de- posited they are white, but that they soon blacken. They are boat-shaped, and one end is slightlj^ deeper and fuller than the other. The thickening at the edge, which in pre- vious paragraphs was called the clasping membrane, is 108 MOSQUITOES composed of air chambers, and is used to keep the hoat- shapod eg-g with its flat surface uppermost. The Eiig-lish writers have observed that when the eggs have been much rubbed, the delicate membrane splits off and the eg^ ap- pears with a glistening black surface like patent leather. They have noted also that when the egg, as frequently happens, is drawn by capillary action a little way up from the water on a leaf, the head or blunt end always points downward, so that when the larva emerges it drops into the water, and not up in the air. Grassi says that the eggs of this species lie in groups of from three to twenty, side by side, like a bridge of boats, but Nuttall and 81iiple\' find them in open pools in Great Britain scattered about. According to these observers the eggs hatch on the second or third day after being laid, depending on the temperature, the young issu- ing through a circular split near the blunt end of the egg. Thej^ also state that eggs which were dried less than five days did not hatch. Full and detailed accounts of the anatomy of tlu^ larva and pupa arc given by the English writers in a paper entitled "The Structuri^ and Biology of Anopheles " {A. niaculipeiniifi) in the Jounuil <>/ ITinjlene, vol. i.. No. 1, January, 1901 ; this article is beautifully illustrated. Fig. 2.J — Head of Full- grown Larva of AnopJieles ptinc t, i- pen /lis ; e n 1 a r g c d. (Author's illustra- tion.) THE MALARIAL MOSQUITOES 109 Natural Breeding- Places of Aiioplieles. A number of the natural breeding-places of Anopheles niacuUjiennis and A. pmictqicnnit^ have been found by the writer in the United States. They have always been found in more or less permanent pools of water, either in the bed of an old canal or in spring-fed woodland streams, or in the side pools or shallows of field spring-s, or in artificial excavations filled with surface water. In such places, when supplied with a certain amount of green scum, the little larvje will often be found resting at the surface of the water, and occasionally darting from one spot to another. The larvae of A. j^uit^ctijwinis ditier from those of A. tiia- culipennis largely in the marking of the head, as indicated in the accompanying figure. Tlie temperature of the water which they inhabit varies from 18° C. to 25° C- Nuttall and Shipley state that in England these larvae are to be found in pools, ditches, backwaters of rivers and canals, and in other slow-flowing waters ; almost in- variably in such waters as are clear and very rarely in im- l^ure or brackish water. In their experience, they jjrefer pools which are not shaded by trees, althougli I have found them in this country on several occasions in a dense shade. They are very rarely found in water con- tained in barrels and troughs and fountain basins, and they are very rarely found in the same water with the larva) of Culex. Mr. E. E. Austin, in " The Eeport of the Proceedings of the Expedition for the Study of the 110 MOSQUITO I'JS Causes of Malaria at Sierra Leone," states that on August 20, 1891), Dr. Prout and Dr. Berkeley found Anopheles larvse mingled with those of Cnlox in a tub of Fig. 2G.— Feiiiiile of Anopheles puiictipetinis ; eulargocl. (Autlior'.s illus- tration.) water in a yard at the Sanitary Office. With one excep- tion this is the onlj^ instance in which he found Anoph- eles breeding- elsewhere than in a roadside puddle or ditch. Dr. C. W. Daniels, in the " Royal Society Reports THE 3IALABIAL MOSQUITOES 111 to the Malarial Committee," December 31, 1900, says that in Africa either larva3 may be found alone, but in many situations both are found together and even several spe- cies of each. At least five species of Culex were found with Anopheles larvae. " The less the movement of the water the greater the probability of Culex larvae being also found, and in a grass-grown river, the Anopheles FiG_ 37.— Male of Anopheles puneUpcnnis, from side ; enlarged. (Orig- inal.) larvae will be more abundant near the stream and the Culex larvae near the bank." Nuttall, Cobbett, and Strange way s-Pigg, in England, captured Anopheles nine times with Culex in ponds and also took them with Culex in ditches in which the water scarcely flowed, in water-logged boats, in stone troughs, and in fact found them fourteen times together with 112 MOSQUITOES Culex and tcu times with lisli. Dr. F. A. Young, a Brit- isli army sur<:;con, lias told mc that in his experieuce if the larvie of Culex and Anopheles are put into the same vessel those of Anopheles will disappear. Lieuteuaut-Colonel Yerbury says that " the natural liome of Anopheles seems to be damp swampy ground, but not necessarily so wet as a marsh or a fen." Grassi and Fiealbi state that A. niacidlpinmh is most frequently found in flat land in Italy, the larvie requiring clear water rich in vegetable food. E. E. Austen found in Freetown that Anopheles larvie were iu stagnant puddles, varying from a foot to several feet, at the sides of the streets, but many were met in the still water in little bays at the side of slowly running shallow ditches. Whether the w'ater was clear or muddy seemed to make no difference, but green algaj were nearly always present and in some pud- dles tadpoles were numerous. Dr. H. A. Veazie, of New Orleans, has found Anopheles larvie in the ponds out in the suburbs iu the swamps back of the city. Dr. Wol- dert, of Philadelphia, has found the larvie of both ^1. ma- carqwnnis w\\i\. A. inuict'ipcnn'is breeding in the same nar- row and slowly flowing stream of fresh water, which drained a marshy district formed by a raih\)ad end)ank- ment. He found larva' in this stream from June lOtli to November 11th and located live localities within the city limits of Philadelphia where Anoi)heles breeds. Grassi, at Metai)onto, Italy, is said to have found Anopheles in brackish water. THE 3[ALARIAL MOSQUITOES 113 The North American Species of Anopheles. So far as known at the present time we have but three species of the mahirial g-enus in the United States, namely A. rnacuUpetirds Meigen (equals A. qaadmiiaculatus Say), A. 2Ju?ictipe?in:is Say, and A. crucians Wied., although Mr. Theobald, in his monograph, which will include the mos- quitoes of the world, will describe forty-two species of this genus, and possibly more. A. 7/iaculi2)en7m is a rather insignificant species, which is well illustrated in Figure 15, its wings being nearly clear, but marked Avith four rather small dark spots composed of groups of darker scales. Its palpi are entirely black. A. 2>(nidi2Miuiis is our handsomest species, and has a yellowish white spot occupying about three-fourths of the length of the front margin of the wing. The scales on the last vein are white and those at each end black. A. crucians has the palpi marked with white at the bases of the last four joints, and the scales of the last wing vein wliite, marked with three black spots. The ac- companying figures will enable a much readier differentia- tion of this species than will any description. As to distribution,^. 7)iaculipen?iis and A. 2nincti2)ennis are found almost everywhere in this country. I have seen specimens of A. maculi2yennis from New Hampshire, Con- necticut, New York, District of Columbia, Maryland, Vir- ginia, Florida, Texas, Louisiana, Indiana, Illinois, Min- nesota, and Oregon. Dr. A. S. Packard has recorded its 114 NOSOriTOES occurrence at Brunswick, Me., in 18<)l-63. A. ininctipen- nis I have seen from Vermont, Massachusetts, Connec- ticut, New York, New Jersey, Pennsylvania, District of Cohimbia, Maryland, Mississippi, Texas, New Mexico, Yiv,.'i'6—Ani>j)hiles crucians, adult feinaU' ; eulargod. (Aiithui'.s il- lustration.) Kansas, Illinois, Indiana, Orej^on, and Jamaica (13. W. I.). Professor C. H. Feruald writes me that he has taken it at Orono, Me., and that it is rather common at Amherst, Mass. A. crucicam I have seen only from the District of THE MALARIAL MOSQUITOES 115 Columbia, Virginia, Georgia, Florida, and Louisiana. The last species therefore seems to be a more southern form, while the other two have a very wide distribution, including- a considerable distribution to the North. Dr. W. N. Berkele}^, of New York, in the Medical Record for January 26, 1901, states that A. j^^inct'qyennis is abun- dant in certain parts of Bronx Boroug-h, particularly Je- rome Park. A. inacidipennis api)ears to be universally dis- tributed in the suburbs of New York. Since he learned how and where to look for it, he found it nearly co-exten- sive with all the cases of fresh malaria that he had the leisure to g-o to and look into. It was present in such widely separated places as Passaic, N. J., Tuxedo, New York, Fordham, and Jerome Park, Mount Vernon, and East Hampton. In East Hampton, on the authority of Dr. F. P. RoUey, Dr. Berkeley says that until the summer of 1900 no native malaria had been known at East Hamp- ton, in spite of a larg-e number of malarial mosquitoes. He explains this in two ways : (1) That no malarious case had recently been imported there to start an infection among- the mosquitoes, and (2) that the nights are cold, the night temperature being considerably below the mini- mum (77° F.) at which the malarial bodies are believed, according to Koch, to develop in the stomach of the mos- quito. The Anopheles Avas always found in buildings, oftenest on walls and ceilings of reeentl}- used bedrooms, and far most abundantly in the foul and ill-ventilated bedrooms of the poor. The house females were usually gorged with blood, and sluggish enough to be easily caught. They were numerous in outdoor privies. He IIG MOSOriTOliS never found them out of doors. Males were cau<,'-ht in houses also, but generally only one male to twenty Fi(i. 29. — Anopheles argyriturds, :i(hilt fcinalf ; (.'iilarm.'il. (Original.) females. He cau<.,'"lit Anoi)lieles in a house in the Bronx on November Gth and on Christmas day. In a draughty, cold, underground cellar in the same house he caught a dozen THE 3IALARIAL MOSQUITOES 117 or more, all females, mostly punctipe?i?iis and a few maculipermis. They were iu complete hibernation, and had to be knocked from the wall as if dead, but revived in a glass tube under the warmth of the hand. So far as Dr. Berkeley's observations go, the hypothesis of the Italian workers that only fertilized females survive the winter, is true. Dr. Theobald Smith, of the Bussy Institute, has pub- lished a paper entitled, " Notes on the Occurrence of A7iopheles pundipennis and A. quadrimaculatus in the Bos- ton Suburbs," in the Journal of the Boston Society of Medi- cal Sciences (vol. v., pp. 321-324, January, 1901) in which he shows that he has found both species at Jamaica Plain, although malaria does not exist there. The oc- currence of the Anopheles, unless their breediug--places are wiped out, shows that if malaria patients should come to Jamaica Plain, the disease would rapidly spread. The species Anojiheles argyritarsis, mentioned in Chap- ter X. and illustrated in Fig-. 29, is a very beautiful species which occurs in Cuba, where it has been captured by Dr. James Carroll of the Army Yellow-fever Commission, Food of Anopheles Larvae. As already indicated, the principal food of the larvae of Anopheles seem to be the spores of algae, but, as Ave have pointed out, they will swallow anything which floats on the surface of the water. I have seen one nearly choke to death in the attempt to swallow a good sized bit. The English observer, Dr. Daniels, in the course of his in- 118 MOSQUITOES vestig"atioiis in Africa, fouiid that tlic contents of the intestines of the hirviT> arc mainly vegetabh' matter — in some cases entin^ly so. Occasionally limbs of minute in- sects or crustaceans were found, as well as scales of mos- quitoes or other ins(X'ts. " On watchiui;- them feeding- it is seen that all minute jiarticles are drawn to the mouth, but many of them are rc^jected. This rejection is some- what arbitrary, as a particle at first rejected is often subsequently swallowed. Among the bodies seen to be swallowed I have seen living minute crustaceans and young larva', both of Anopheles and C-ulices, but as a rule living animals either esca[)(^ or are rejected." Chris- tophers and 8tei)liens state that in their ol)servations in Sierra Leone the food of the majority of the Anopheles larvse seemed to be a unicellular protococcus. Length of Life of Adult Anopheles. Physicians studying the adults in order to d«^termine tlu^ duration of the different stages of th(» malarial organ- ism have occasion to keep adult Anoi)heles alive in con- finement. This has been accomplished up to eight weeks 1)V feeding tlnnn occasionally upon sliced bananas or otluu' fruits. The adults live for very considerable si>aces of time, as has, in fact, been pointed out in the first chap- ter of this book. In colder climates the adults hibernate often in houses, and in trojucal climates the adults live through the dry spell to lay their eggs when the rains come and breeding-pools are re-established. The hiber- nation of Anopheles in this country has Immmi fi-tMpicntly THE 3IALJBIAL MOSQUITOES 119 observed. Dr. W. S. Thayer has informed me that he found Anojyheles crucians and Anojyheles r/iaculi^yemiis hibernating- in enormous numbers in barns near New Orleans, and in early February, 1901, Dr. H. A. Veazie wrote me that A?iopheIes pu,nciipe?mis had been captured in his house, in his office, and in the show-window of a shop on Canal Street. Dr. A. Hassel, of Baltimore, found Anopheles j^'^'nciipenms in his house in January, 1901, and during- this month his son and daughter developed ma- laria, the diagnosis being- perfectly confirmed by blood examination. About a Aveek before this were several warm days. Probably the mosquitoes had been hibernat- ing in his house and had become active on account of the warm spell. How Anopheles Bites. It is the experience of a numlier of observers, as re- corded, that the bite of Anopheles is more insidious than that of Culex. "When not occurring in numbers, they may bite a person while asleep and not be detected. This point is especially used in answering the broad and general statement that malaria may be developed where there are no mosquitoes. Professor E. W. Hilgard, of the University of California, wrote me in September, 1900, to the effect that in the coast marshes of the Missis- sippi Sound, he has seen Anopheles in great numbers, probably pimctipennis. Down there this insect is called the black mosquito, and, as Professor Hilgard states, " is noted for biting without a moment's reflection, plunging 120 JfosnriToi'JS head foremost riqbt iuto you, while Culex always medi- tates for a while before biting-." Professor Hil^'ard further stated that iu those marshes there is little or no malaria and that he had been exposed there for weeks without injury, nor did the iidiabitants complain of chills or fever. But in the Arkansas bottoms it took him only a few days to succumb, and the natives "luxui'iated in ' asTue cake.' " Mosquitoes and Yellow Fever ; Mosquitoes and Filiariasis IN 1881, Dr. Carlos Finlay, of Havana, noticed a cor- respondence between the abundance of mosquitoes and a period of increase of yellow fever in the autumn, while during- the summer yellow fever had been scarce and mosquitoes also scarce. This sug"g"ested to him the idea that mosquitoes are responsible for the transfer of the disease, and he conducted certain experi- ments in which he claimed to have transmitted the disease by the bites of the mosquitoes which had previ- ously sucked the blood of persons suffering' with the disease. Carrying on his idea further he proposed a plan of inoculating non-immunes by the bites of infected mosquitoes, on the theory that a mild type of the disease would be produced which would afterward be protective against reinfection of a more severe character. Dr. Finlay's theory w^as received with interest by phy- sicians and investigators, but with a very pronounced g-eneral incredulity. His experimental work did not seem to have been definite enough to attract confidence to his conclusions, nor was there enough of it. It is 121 122 MOSQUITOES rather strange that his published papers did not excite sufficient interest to induce other investigators to under- take any experimental work in the same direction. This fact in itself shows plainly the almost perfect incredu- lity with which they were received. When, however, the l)oautit'ul results of the malarial investigators had become g"cnerally accepted and it was shown beyond all peradventure that not only do certain mosquitoes carry filiaria, but also that some of them are necessary second- ary hosts of the malarial micro-org-anisms, then it was that a few people began to think of Dr. Finlay and his theory. In the meantime, strong efforts had been made to find the cause of yellow fever. Several micro-organ- isms had l)een discovered and several investigators announced the probable discovery of the causative germ. Nearly all of these discoveries have been discredited by subsequent observations. The organism which has received the most support has been the BaciUus icteroides of Sanarelli, but down to a very recent date the insistent claim by the Italian investigator of the value of his dis- covery has been disputed by competent observers. The occupation of the island of Cuba by American troops attracted the attention of Dr. Stcn'uberg, Surgeon- General of the Army, more strongly than ever before, to the subject of yellow fever, although he had long been an ardent investigator of the cause of the disease, and, in fact, was one of the Yellow-fever Commission who visited Cuba in 1870, in an effort to investigate scicmtifically and by modern bacteriological methods tho causation of the fever. In this earlv Cuban residence he became ac- 3I0SQUIT0ES AND YELLOW FEVER 123 quainted with Dr. Finlay and with his mosquito theory, and therefore, under these late conditions and with the malaria case proven, he established a commission of army surgeons, composed of Major Walter C Heed, Surg-eon, U. S. A., Dr. James Carroll, Acting- Assistant Surgeon, U. Fig. 30.—St(go7nyia fasciata, ndult female ; enlarged. illustration.) (Author's S. A., Dr. Jesse W. Lazear, Acting Assistant Surgeon, U. S. A., and Dr. A. Agramonte, Acting Assistant Sur- geon, U. S. A., and instructed them to investigate the disease from the mosquito standpoint. The investiga- tions carried on by this commission during the early 124 MOSQUITOES part of 1900 were extremely sugg-cstive in their results. In the course of the investigatious, both Drs. Carroll and Lazear were attacked by the disease. Dr. Carroll recov- ered, but Dr. Lazear died — another of the lon^ list of martyrs who have suffered in tlu^ cause of scientific research. In this iircliininary work, which Dr. Heed reported upon at the twenty-eighth annual meeting- of the American Public Health Association, Indianapolis, Ind., October 23, 1900, it was shown that eleven non- immune individuals had been inoculated by the bites of the species then knoAvn as Cvl c.r faHc\atas,vA\\c\i had previ- ously fed upon blood of jiatients sick with yellow fever. Dr. Reed was abk; to report two positive results in which an attack of yellow fever followed the bite of a nioscpiito within tli(^ usual period of incubation of the disease. In one of the cases all other sources of infection could posi- tively be exclud(Ml. The results of this preliminary work were summed ui) in two conclusions : 1. Bacillus idc- roides Sanarelli stands in no causative relation to yellow fever, but when present should be considered as a second- ary invader in this disease. 2. The mosquito serves as the intermediate host for the parasite of yellow fever. The announcements made in this preliminary note ex- cited much attcnition. The scientific standing of the in- vestig-ators, as well as the positive result announced in one of the cases, made the theory at once one of serious importance. Medical men, however, were inclined to wait for further developments bef expressing an o]>inion. Their point of view was jierhaps W(>11 summed up by the J^ritiiih Miiliail Jouriud, which stated that althougrh the 3I0SQU1T0ES AND YELLOW FEVER 125 experiments "appear to show almost conclusively tliattlie g-erm is conveyed by a special species of mosquito and tliat the insect becomes infected only after ten to thirteen days from the time of the ingestion of the germ, the ex- periments are really by no means conclusive. At the most they are suggestive." But the investigators themselves were by no means satisfied with the proof which they had gained. They returned to Cuba in the autumn of 1900, and spent the re- mainder of the autumn and the whole winter in further exi)erimental work. The results obtained were so i^osi- tive and striking- that, with the permission of the Sur- g-eon-General, they presented an additional note before the Pan-American Medical Congress, held in Havana, February 4-7, 1901. This paper, presented by Major Reed, records the details of the work done up to that time and announces its results. An ex])erimental sanitary station was established in an open, uncultivated field, about one mile from the town of Quemados, Cuba, under the complete control of Major Reed. The station was named Camp Lazear, in honor of the brave physician who went to his death in the early summer of 1900. A most careful series of experiments was carried on to see whether yellow fever can be con- veyed by fomites, that is, by personal contact with the clothes or belongings of yellow-fever patients. As is well-known, the consensus of opinion, both of the medi- cal profession and of others, is in favor of the conveyance of yellow fever in this way, and every effort is made to disinfect clothing- and bedding- shipped from ports where 126 MOSQUITOES yellow fovor prevails. All articles of personal apparel are subjected to disinfection and, as everyone knows, durinj^ a time when the fever is epidemic in any of our Southern States even the mails are disinfected before being* allowed to go North. There was further erected at C'amji Lazear a small frame house with a cubic capacity of 2,800 feet, tig-htly ceiled and battened, provided with small windows, so as to prevent a thorough circulation of air through the house, and with Avooden shutters to prevent the disinfect- ing qualities of sunlight. The windows were closed by l)erniauent wire screens with a 5-millimetre mesh. The vestibule was protected by a solid door and a wire screen- door, and the inner entrance by a second wire screen- door. In this way the passage of mosquitoes into the room was ettectuall}" excluded. The average temperature Avas kept at 7G.2° F. for a period of sixty-three days, and precaution was taken to maintain suthcient humidity of the atmosphere. On November 30tli, three large boxes tilled with sheets, pillowslips, blankets, and so on, con- taminated by contact with cases of yellow fever and their discharges, were received and placed in the room. Most of these articles had been taken from the beds of i)atients sick with yellow fever in Havana. Manj' of them had been purposely soiled with the excretions of i)atients. These soiled sheets, i)illowcases, and blankets were used in preparing the beds in which the members of the hos- pital corps slept. During sixty-three days this building, thus furnished, was occupied by seven uon-immuue per- sons. Three of them occupied the room each night for twenty days. Later a fourth box of clothing and bed- MOSQUITOES AND YELLOW FEVER 127 ding- was added, some of it purposely soiled with the bloody stools of a fatal case of yellow fever. Two of them occupied beds from December 21st to January 10th, every nig-ht, wearing the very garments worn by yellow-fever patients throug-hout their entire attacks, Fig. 31. — Strgomyia fdsciata, adult male ; enlarged. (Original.) making use exclusively of their much-soiled pillowslips, sheets, and blankets. At the end of twenty-one nights they went into quarantine (as had the former three) and were released five days later. Two other non-immunes occupied the same bods for twenty days more. The at- tempt therefore which was made to infect this building 128 MOSQUITOES and its seven non-ininiune occupants during' a period of sixty -three days was an absolute failure ; all seven were released from quarantine in excellent health. A precisely similar building was erected at Camp La- zear, which was known as the infected mosquito building. The door and windows were placed on opposite sides of the building so as to give a thoroug'h ventilation. It was divided into two rooms by a wire screen partition extend- ing- from floor to ceiling. All articles admitted to the building were carefully disinfected by steam before be- ing placed therein. Into the large room of this build- ing mosquitoes which had previously been contaminated by biting yellow-fever patients were admitted. Non- immunes were j)laced in both rooms. In the room in which mosquitoes were not admitted the experimentalists remained in perfect health. In the other room six out of seven persons bitten by infected mosquitoes came down with yellow fever. In all, of persons bitten by infected mosquitoes that had been kept twelve days or more after biting yellow-fever patients before being allowed to bite them, eighty per cent, were taken with the disease. The conclusions reached after this careful experimen- tation, have been summarized under eleven heads, as follows : 1. The mosquito — C. fascidtas — serves as the intermedi- ate host for the parasite of yellow fever. 2. Yellow fever is transmitted to the non-immune indi- vidual by means of the bite of the mosquito that has previously fed on the blood of those sick with this dis- ease. 3I0SQUIT0ES AND YELLOW FEVER 129 3. An interval of about twelve days or more after con- tamination appears to be necessary before the mosquito is capable of conveying- the infection. 4. The bite of the mosquito at an earlier period after contamination does not appear to confer any immunity against a subsequent attack. 5. Yellow fever can also be experimentally produced by the subcutaneous injection of blood taken from the general circulation during the first and second days of this disease. 6. An attack of yellow fever, jDroduced by the bite of the mosquito, confers immunity against the subsequent injec- tion of the blood of an individual suffering from the non-experimental form of this disease. 7. The period of incubation in thirteen cases of experi- mental yellow fever has varied from forty -one hours to five days and seventeen hours. 8. Yellow fever is not conveyed by fomites, and hence disinfection of articles of clothing, bedding, or merchan- dise, supposedly contaminated by contact with those sick with this disease, is unnecessary. 9. A house may be said to be infected with yellow fever only when there are present within its walls contami- nated mosquitoes capable of conveying the parasite of this disease. 10. The spread of yellow fever can be most effectually controlled by measures directed to the destruction of mosquitoes and the protection of the sick against the bites of these insects. 11. While the mode of propagation of yellow fever has 130 MOSQUITOES now been definitely determined, the specific cause of this disease remains to l)o discovered. A larg-e supply of contaminated mosquitoes, carefully preserved, has been brought to Washing'ton by Drs. Keed and Carroll and careful work is now being carried on in an effort to find the causative organism of the dis- ease. It seems quite probable that it will prove to be some sporozoon, following in a measure a somewhat similar life-round to that of the malarial organisms. It is interesting to note that the very recently pub- lished " Interim Report " of Herbert E. Durham and the late Walter Myers, to the Liverpool School of Tropical Medicine, based on observations on yellow fever in Bra- zil, in the course of which Dr. Myers died, just as did Dr. Lazear in Cuba, indicates the belief of these investigators in the causative effect of a small bacillus which they found in the organs of ail fatal cases. They conclude that the yellow fever is not due to a protozoon, and with regard to the American results, they make the following comment : " The endeavor to prove a man-to-man trans- ference of yellow fever by means of a particular kind of gnat, by the recent American Commission, is hardly intelligible for bacillary diseases. Moreover, it does not seem to be borne out by their experiments, nor does it appear to satisfy endemiological conditions." It is obvious that this report of the English investigators was prepared before the final and more complete paper of the American Commission was read by Dr. Heed in Hava- na, and even with this granted, it was hardly fair in them to style the investigations of the Americans " an endeavor MOSQUITOES AND YELLOW FEVER 131 to prove," etc. The Americans were after the truth, and had no desire to learn anything but the truth, that is to say, they did not endeavor to substantiate any particular theory. As a result of the investigations, the Governor-General of Cuba, himself a medical man. General Leonard Wood, became so impressed Avith the accuracy of the conclu- sions that he authorized the promulgation of instructions to commanding officers in Cuba, relative to protection against mosquitoes and remedial measures in connection with their breeding-places. General orders were issued requiring the enforcement of the use of mosquito bars in all barracks, and especially in all hospitals, and the de- struction of the larvaj by the use of petroleum on the water where they breed. (See Chapter VIII.) The medical offi- cer who makes the sanitary inspection at each post is charged with the supervision of the details of these pre- cautions. As a result, the writer understands that the prevalence of malaria has been greatly reduced in western Cuba, and it is hoped that with regard to yellow fever similar results will be shown during the coming year. The Yellow-fever Mosquito. The particular species of mosquito Avhicli was used by Dr. Finlay in his original experiments, and which is the only form which has been shown by our Army Commis- sion to transmit the disease, is the one which has been referred to in this country as Culcx fasciatus Fabricius. It was so termed in the writer's bulletin, entitled "Notes on 132 MOHQl'ITOHS Mosquitoes," pul)lishotl as Bulletin 25, new series, of the Division of Entoinoloi^y, of the United States Department of Ag-riculture, Au^^ust, 1900, and lias been so named in the published reports of the Commission. There now seems very good ground for the belief that the wide-spread Fig. 32. — Adult ]\I.ilf of Stefjoiuyio fnsciatn from side ; enlnrncd. (Aulhor's illu.slnilioii.) tropical mosquito usually referred to as Ctder td'nidtvs of AN'iedeniann, is really a synonym of this speeies. It will be remembered that down to the present time we have no evidence that any other moscpiitoes than those of the genus xVnopheles transmit nndaria, and that so far as known all species of this genus have this ijathological MOSQUITOES AND YELLOJV FEVER 133 characteristic. In the case of yellow fever, why should one species of Culex be able to transmit the disease and not another species, assuming, as it will be quite proper to assume, that since this capacity appears to be of generic importance with Anopheles, it would be of generic im- FiG. 33. — Body Scales from Stegomyia fasciata ; tlie broad one from a white stripe and the narrow one from a ilarlc surface ; greatly en- larged. (From Photo-micrograph by Dr. Erwin F. Smith.) portance in the case of yellow fever ? It happens that the British Museum is investig-ating- the mosquitoes of the world. Specimens have been sent to the expert, Mr. F. V. Theobald, who has charge of the work, from all quar- ters of the globe, and Mr. Theobald has made a special 134 MOSQUITOES study of the morplioloy-iciil f(\'itures of these iusccts. Without knowiiii;- the results of the American Commission, Mr. TheobakI had decided that Culex fascinius or fxes are fonnd side by side, and are capabh^ of livini;- there a lonii' tinu'. They ob- struct at certain points the flow of the lymi»h. This ac- cumulates and dilates the vessels and ilic lyiupli.ilic spaces. This mechanical distention is accompanied by an irritation of the vessels and of the surroundinir con- ned ive tissue. Thus, eh^jihantiasis ])ecomes established, which, as is ^'enei'ally known, manifests itself in very dif- fei'ent deq'rees and occui)ies ditlt'erent ])arts of the body, such as the arm, the lere unknown except in i\\v adult condition, this consideration must necessarily be brief. Genus Psorophora Desvoidy The insects of this genus are large mosquitoes, and only one species, l^oropliora c'dlaia of Fabricius, inhabits the United States. In this insect the paljn in the male are long-er than the proboscis, while in the female they are less than one-half as long as the proboscis. The 144 OTHER GENERA OF 3I0SQUIT0ES 145 proboscis itself is straight. The most striking charac- teristic, hov/ever, is the presence of very peculiar erect scales ou the legs. The hind legs especially are fur- FiG. 37. — Adult Female of Psorophora ciliata ; enlarged. (Author's illustration.) nishecl Avitli large scales which are placed at right angles to the leg itself, and similar scales are present in smaller numbers upon the middle logs, and in very small num- bers upon the end of the thighs of the front legs. P. 140 MOSQUITOES ciUata is a very lai'S"o mosquito and is undoubtedly one of the forms known in the South as in large battery jars, under condi- tions which had rei)eatedly been successfnl w ith nu^scpiitoes of the genera Cnlex and Anoi)heles, bnt no eggs were deposited. 'I'his Itronght me to tlu^ concbision that either the confined specinn-ns were not impregnated or that they had already de|)osited all their eggs, or that their biceding lial)its ditler from those of othei- moscpiitoes. On August ;5(lth some very large mosquito larvae and pupie were received from Mr. Fic. 10. -"^'diiMU' Larva nt' J'somph- orii cilidtd : (■iil;n_i;v(l. (Aulliur's illusliatioii. ) OTHER GENEBA OF MOSQUITOES 149 William P. Seal, of the Aquarium Supplj' Company, :.t Delair, N. J. On examining- them I felt sure that they Fig. 41. — Full-grown Larva and Pupa oT I'.-inrnpliord ci/iafK. with on- larged parts; enlarged. (Author's illnstralion.) could be nothing less than the larvje and pupsie of Psoro- phora cUlata. The first s]iocimens received were in alco- hol, and Mr. Heal was informed of their j)robable identity, 150 MOSQUITOES and urged to send on living* specimens in water, and to en- deavor to rear the adult. It was then, however, uiifor- tnnat(^ly, too late. He wrote that during the summer a small creek and some earth ponds on his place became entirely dry, in consequence of which all fish in them died. Some time in Aug'ust there was a sufficient rainfall to fill a few of the deepest places, which soon after be- came almost alive with mosquito larva). These were used for fish-food, until it was noticed that they were develop- ing to the pupa stage, when coal oil was immediately poured on the water. It Mas while the coal oil was be- ing applied that the big larvre and i)up;e were first no- ticed. Mr. Seal had been a collecting naturalist for twenty-six years, supplying material for the aquarium and for biolog"ical research, and had discovered some low forms of life new to science, which were described by Leidy and Ilyder, but in all his experience he had never seen such large mosquito larva\ On being assured of the novelty and im[)ortauce of his observation, he promised to watch for the subsequent a]i])earance of similar larvsio, and on Sejitember 20tli found other specimens which appeared after a rain which occurred on September 15th or a little Ijefore. Mr. Seal was able to distinguish between them and the Culex larvjTp, and wrote that they were very scarce — per- haps one of them to many thousands of the others. On Septemljer 25th additional larva) and ])ui>a) were sent in, and from these specimens the accompanying illustra- tions were made. The larva is structurally of great interest. On com- OTHER GENERA OF 3WSQUIT0ES 151 parisou with larva of Culex, Avliicli it resembles more nearly than that of Anopheles, it will be seen that the breathing tube is longer ; that the anal flaps are longer and more pointed, and the hair fringe on the under side of the last segment of the body is much longer and denser, while the mouth-i^arts are quite different. Tlie jaAvs are sharply toothed, and very long, and are used in the mastication of food. Other mosquito larvfe feed upon spores of alga3 and other small particles which appear to require no mastication, but this larva descends to the bottom of the water and has been noticed to grasp a bit of water-plant half an inch long and actually to chew it. <■ The duration of the pupal stage was from four to live days, and the adult insects issued on September 27tli and 28th. Young larvae were also found in this sending, and one of them is shown in Figure 40. The breeding-places in which these larvae were found were small depressions in the bed of a small stream, and similar hollows in certain small ponds, all of which were dry the greater part of the summer. After they first dried in the spring they were barren of fish and vegeta- tion. Mr. Seal is satisfied that the insect is rare in the vicinity of Philadelphia, and thinks that possibly he may have brought this species from the South, as he is in the habit of shipping large quantities of aquatic plants from the South, from January 4th to about May 10th of each year. He has a place some miles from Delair where he grows Cabomba. The plant is very dense, and the creek is full of fish, but in the water on top of the plant, which grows to the surface, are large numbers of mosquito 152 MOSQUITOES larvno. Tlie}^ are out of sii^ht and practically out of roach of the lish. The eg-g-s of this interesting mosquito arc yet to be found, and it will bo most interesting to see in what re- spects they ditfer from the eggs of Culex and Anopheles. Genus Megarhinus Desvoidy. Another of the large mosquitoes w^liich seem to be col- lectively known in the South as gallinippers (probably also some of the harmless crane-Hies are so dublx^l) belong to this genus. In fact there are two of them known in North America, namely Jfcgarhinus Juvmer- 7'hoidalis F. (Mexico and Cuba), and M. ihtrtoricensis Roeder (Mississippi). These mosquito(>s also should be investigated by Southern observers in regard to their possible connection with malaria, or some other l)lo()d disease. They are readily distinguished from other mos- quitoes by the curved beak. The palpi in the male are as long as the proboscis, but are short in the female. The colors are bluish or greenish. Nothing is known of the life history of the mosquitoes of the genus Megarhinus, and some Southern ol)serv('vhas an admirable chance to add to tlie sum total of liuiiian knowledge by a series of careful observntiims on one of these forms. OTHER GENERA OF MOSQUITOES 153 Genus Aedes Meigen. The mosquitoes of tins o-enus are minute forms, insig-nif- icaut in color, and apparently rare. One species, Aedes fuscus Osten Sacken, has been found at Cambridge, Mass. Fio. ^2,.— Atdes fuscus, female ; enl:irt,^e(l. (Author's illustration.) Aedes fuscKS, according to a recently published note by Dr. J. B. Smith, has been reared by Mr. J. Turner Brake- ley at Horuerstown, N. J., from larvie found in the pitchers 154 MOSQUITOES of the pitcher-plant {Sarracenia). The determination was made by Mr. C. W. Johnson, of Philadelphia, and is there- fore undoubtedly correct. Fui. 43. — To-vd'hyiichites rnlihis, female ; CLlaiged. (Author's illiislration.) As i)ointod ont in the sj^noptic tables in Chapter X. the pali)i in both sexes are short, Avhit-h disting-uishes these little mosquitoes from other North American forms. OTHER GENERA OF BIOSQUITOES 155 Stegomyia, Toxorhjnicliites, Uranotsenia and Concliyliastes. As will be pointed out and fully explained in Chapter X., these four generic names are here used for certain American mosquitoes for the first time. I am able to use them in this book throug-h the great courtesy of Mr. F. V. Theobald, of Wye, England, who has sent me proof sheets of his monograph of the mosquitoes of the world, now being published by the British Museum. Stegomyia includes, as has already been shown, the yellow-fever mosquito, S. fasciata, and it also includes the species mentioned in my previous writings as Cidex signifer Co- quillett, and which has been captured in the District of Columbia and Virginia by Messrs. Coquillett, Barber, and Pratt. Toxorhynchites includes the species previously referred to as MegarJiinas rutilus and which must now be known as Toxorhyncldtes rutilus. Uranotsenia includes the North American species previously known as Aedes sap- jy'n'Jiinus. Concliyliastes includes two species formerly j)laced in the genus Culex and which must now be known as Conchyliastes musieus Say and (J oneJiyJ tastes posiicatus Wied. The former species has been taken in Pennsjdva- nia, Virginia, District of Columbia, and Texas by Messrs. Johnson, Pratt, Thayer, and Barber. YII Nil fund /'Jitcni'ics of Alosr/fflfoes WHEliE mos(|uitoes exist in rain-water l)uc'kets and l)arrels they are apt to have none or very few natural enemies. Their principal enemies when in the aquatic larval and pupal stages are fishes and carniv- orous insects. Most carnivorous insects are rather slow breeders, and as a consequence they seldom deposit their eg-g-s except in rather permanent pools, and naturally fish are found only in such places. There are, however, other enemies aside from these. Dr. C. W. Stiles informs me that during the summer of 1889, when working with C. H. Hurst, they collected at Leipsic a large number of mosquito larvno and pupno, and that many of them died in the laboratory. Upon opening one of the bodies, which was quite distended, he found a species of Mermis, one of tlie hair Avorms or hair snakes, coiled up in the body cav- ity. Examination of other dead larvjTO or ytnpiv disclosed the fact that nearly every one was ])arasitized by the same sj)ecies of Mermis. He showed the worms to Professor lAudolph Leuckart, who inrormed him that he had re- peatedly found the same Nematode in former years, and that he had observed that in years wIkmi mosquitoes were numerous the worm is very scarce. This h'd him to be- 156 NATURAL ENEMIES OF MOSQUITOES 157 lieve that the parasite was a not unimportant factor in destroying- mosquitoes near Leipsic. Later, Dr. Htiles found the same worm in mosquito larvie and pu})* taken from other breeding'-phices, and it was quite noticeable that the iJarasitized insects were weaker in their move- ments than those tliat were not infected with the Avorm. In the next summer (181)U) he again looked for the worm, but found none, and it appeared to him that mosquitoes were more abundant that year than in 1889. Dr. Stiles also informs me that a Sporozoan of the genus Glug-ea is referred to as parasitic in mosquitoes, but that Labbe, in his recent monograph of the Sporozoa, does not give Culex in his list of hosts. Dr. Stiles does not recall who found this parasite, nor does he know whether it is of any particular economic importance. By far the most effective natural enemies of mosquito larvae and pupae are fish. Almost all of the small carni- vorous fish which inhabit swamp pools and still water will feed upon mosquito larvae. Nearly all of the minnows, especially those forms knowni as top-minnows, of the gen- era Fundulus and Gambusia, feed abundantly upon in- sects found near the surface of canals, slow streams, mill- ponds, and other similar places, and, although not at all specific in their choice of the early stages of the mosqui- toes, eat them perhaps with even more avidity than other aquatic insects, especially such as are hard-shelled. Then, too, the voracious little creatures known as stickle- backs, and especially the forms known as Gasterosieus acv- leai)i.siiW(\ G. hisphiosii.^ hav(^ this beneficial habit. Stickle- backs, however, are by no means confined to insects for 158 3I0S QUI TOES food, but will feed ui^on other animals, inclndins" prood- sized tadpoles. Anyone who has attempted to keep tad- poles and sticklebacks in the same aquarium will realize the truth of this statement. I once kept a large sized tadpole in the same aquarium with a stickleback, which it exceeded at least live times in size, and its personal beauty was soon sadly damaged by the fact that the sticklel)ack subsisted upon meals taken from the edge of the tadpole's tail. In his previously published bulletin Fig. 44. — Stickleback {Gasterosteus aculeatus) ; somowlial culurged. (After Jordan and Evcrmanii.) on mosquitoes the writer recommended sticklebacks for introduction into fishless ponds to destroy mosquito lar- vae, but Mr. AV. P. Seal, of the Aquarium Supply Com- pany of Delair, N. J., recommends the so-called top-min- nows of the genus Gambusia, common in the brackish waters of the Chesapeake system and southward. He says these are the only tisli he knows which will kill No- tonecta (the water-boatman), but they do this only when other food is scarce, and when the bugs are small. The fish vary in size fn^ii an inch for the males, to about one and three-quarter inches for the females. They live equally NATURAL ENEMIES OF MOSQUITOES 159 well in purely fresh water. He has raised them to the fourth generation in tubs and ponds, and they will breed readily in tubs or aquaria. As destroyers of eg-gs and larvae, and adults as well, of such insects as infest and Fig. 45. — Top-minnow {Gambusia affinis) ; male above ; female below; somewhat, enlarged. (After Jordan and Evermann.) mutilate aquatic plants or lay their eggs in the water, Mr. Seal finds these top -minnows vastly superior to anj^ other species of fish. Dr. H. F. Moore, of the United States Commission of Fish and Fisheries, informs me that the top-minnow, known scientifically as Gatnhuaia affinis, is 160 MOSQl'lTOES abundant in slu.cr.yisli waters, fresh or brackisli, almost everywhere south of the Ohio liiver. It feeds hiryely on vegetable matter, but also on insects. Larval mosquitoes have been found in its stomach. The species is vivipar- ous, as indeed are most of the minnows of this genus, as well as of the geuus Fuiidulus, the young wheu born being about three-eighths of an inch long. It is specially abun- dant in the Gulf States. Dr. H. A. Veazie, of New Or- leans, writes me that this little tisli is common about New Orleans, and that where it is present he has not been able to find mosquito larvie of any kind. He has looked in Fid. 40. — Tdp ininnow {Fundidns notatus) ; sliirlitly oiilurgcd. (After Jonlaii and Evcniiiuin.) gutters and ])onds Avherc to all ajipearances there should bo plenty of larva% and has found none, and very shortly he saw the little minnows patrolling the pools. He says they are great breeders, and ravenous eaters. They are so small that they will go into the shallowest places, and even wriggle on the side of the body to catch their prey. They seem to live under the most adverse circumstances, and do not die until all water is gone. He has seen them so thick in a partly dried-up pond that they had no room NATURAL ENE3IIES OF MOSQUITOES 161 to swim, " yet they seemed happy." As elsewhere stated, they are viviparous, and Dr. Veazie says that a little female will expel large numbers of the young at one time, and that they can be raised in almost anything that holds water. He has seen them swimming around under a layer of ice, as unconcerned and active as they would have been on a hot July or August day. I have been thus explicit in referring to these fish, and have illustrated the best forms, for the reason that a very practical use can be made of them. It was stated a num- ber of years ago in Insect Life, that mosquitoes were at one time very abundant on the Kiviera in South Europe, and that one of the English residents found that they bred abundantly in the water tanks, and introduced carp into the tanks for the purpose of destroying the larvae. It is said that this was done with success, but the well- known food-habits of the carp seem to indicate that there is something wrong with the story. If top-minnows or sticklebacks had been introduced, however, the story would have been perfectly credible, and it points to the practical use of fish under many conditions. Some years ago Mr. C. H. Bussell, of Bridgeport, Conn., described a case in which a very high tide broke away a dike and flooded the salt meadows of Stratford, a small town on the north side of Long Island Sound. The receding tide left two small lakes nearly side by side, and of the same size. In one lake the tide left a dozen or more small fish, while the other was Ashless. An examination by Mr. Russell in the summer of 1891, showed that while the Ashless lake contained tens of thousands of mosquito 162 MOSQUirOES larvfe, that containing- tlio tisU had no hiiva'. Mr. E. A. Schwarz informs me that in Beeville, Tex., a little tish which is known locally as a perch is i)ut into rain-water tanks for this express purpose. There occur on many large estates in the northeast and elsewhere, ponds which are used for Avatering stock. These are sometimes artiticial ponds built with rock bottoms to prevent the exit of the water. They cannot be drained, and on account of their purpose they cannot be treated with kerosene. Into such ponds should be introduced a plentiful siipply of top-minnows or some other voracious mosquito-eating fish. In a later conversation with Mr. Seal, he told me that the top-minnow was suggested because it is a top-feeder, and being very small and slender, it penetrates to the remot- est shallows of the waters which it may inhabit, especially where plants abound and where larvae of mosquitoes are sure to be found. On second thought, he was inclined to think, however, that for general purposes the common little flat suntish, or " pumpkin-seed " as it is sometimes called, would be a good fish to introduce into fishless ponds. It grows much larger, of course, but is very pro- lific, and the young do not make a very great growth in a year, so that the young of each year remain compara- tively small, say from three -fourths of an inch to a half- iuch, until the young of the following year would be ready for business, which would be by July 1st. The top- minnow, he says, being a soft-rayed fish, becomes the easy prey of larger fishes introduced into the same waters, but the suntish, being protected by spiue-rayed NATURAL ENEMIES OF MOSQUITOES 163 fins, enjoys greater freedom from molestation. The sun- fish, he says, abounds in every pond and stream where fish are plentiful, excepting cold mountain-streams. Every aquarium dealer in any large city will be able to supply the common sunfish. Mr. Seal further notes that the common sunfish is the most voracious of the smaller fishes. It has a larger mouth than the top-minnow <^. Fig. 47. — Coniiiion .Siuitish or " Piinipkin-seed " ; reduced. (After Jor- diiu and Everniaun.) and is wholly carnivorous, whereas the top -minnow is omnivorous. On mature consideration, he gives prefer- ence to the sunfish as most completely filling the bill. There are other aquatic vertebrates, besides fish, which destroy mosquito larvae, I am not sure that tad- poles eat them — there seems to be some doubt on that point — but my friend, Mr. Albert Koebele, informs me that he imported into Hawaii from California a large 164 MOSQI'ITOIJS number of the western sjvlain.-iiuler {Dleiiiycfijhis Inrosns Escli.) wliicli were liberated in the iipper part of the Makiki stream in the hope of reducing- the large number of mosquitoes breeding everywhere in small pools and taro fields. He kept two of these salamanders for sev- eral weeks in an open tank, and they devoured, and kept the water free from, the mosquito larvae that bred there. While hundreds of the newly hatclied mosquito larvje could always be observed, none of them ever reached full growth. Mr. Koebele says, "It is to be greatly desired that this valuable batrachian will increase to such niim- bers as to be able to help us keep in check the most troublesome insect on these islands." Then there are many predatory insects which feed upon mosquitoes. The late Dr. R. H. Lamborn, of New York and Philadelphia, was so impressed with the voracity of dragon-flies that he oJBfered a series of prizes for the three best essays regarding the methods of destro\^- ing mosquitoes and house-flies, especially designating the dragon-fly for careful investigation. The prizes Avere awarded and the successful essays were pul)lishod in an entertaining volume entitled " Dragon-flies vs. Mosqui- toes. The Lamborn Prize Essays." None of the essays were able to solve the problem of the practical breeding on a large scale of dragon-flies for mosquito extermina- tion, and, in fact, the insect enemies of the mosquitoes cannot l)e practically handled. Dragon-flies as larva? feed upon mosquito larva^ just as they fivd upon all other aquatic insects and even upon small lish. As winged adults they capture mosquitoes on the wing, just NATURAL ENEMIES OF BIOSQUITOES 165 as they capture other insects on the wing-. The same may be said of other predatory aquatic insects. Some of the aquatic beetle larvfe and some of the predatory water- bug-s undoubtedly destroy hundreds of mosquitoes. Any stag-nant pool, when carefully watched, will l)e found to swarm with predatory animal life. From such a pool I once took a half g-allon of Avater which was teeming with aquatic insects, including- hundreds of mosquito larvae. Among these insects there were three water-beetle larvae of the family Hydrophilidse, and in the course of a week these three larvae practically devoured all of the other animal life in the jar. The adult mosquito also has its natural enemies. We have already mentioned the dragon-flies, and many night- flying birds, such as night hawks and whippoorwills, destroy them on the wing ; and bats, of course, feed upon them. An observation is on record by the late Prof. F. L. Harvey, in Avhicli he states that he found six hundred mosquitoes in the crop of a single night-hawk. In No- vember, 1900, Mr. E. P. Salmon, of Beloit, Wis., wTote me, " There is a parasite, a little red louse, which attacks the mosquitoes on Madeline Island a few weeks after their appearance in June, and from the time this little red louse shows itself on the mosquito under the mosqui- to's wings, the mosquito begins to lose his strength. After a few weeks, along toward the end of July, the mosquito ceases to be very troublesome and seems to be fighting with his parasite for his life." This parasite is probably one of the little red mites which are found upon flies, and particularly upon the common house-fly. 1G6 JKKSQi'lTOJ'JS The mosquito boiiipf an aquatic insect, tlio mito observed by Mr. Sahnon nia}- be one of tln^ little water mites of the family Hydrachnichc, but the nioscjuito issues frt)ni its pupa so rapidly that this is hardly likely. It is more likely to be one of the Trombidiida-, the youn*;- of which ma.y crawl upon the mosquito when it is at rest upon the plants. Some observations upon the natural enemies of the malarial moscpiitoes of the <2:enus Anopheles have l)een made by Dr. C \V. Daniels in East Africa (" lleports to the Malaria Committe(> of tlu^ lloyal Society," Decendier 81, 11)00). He says that tish, and es[)ecially youn^- fry and small fishes, will speedily destroy the mos(juito larva\ but in spite of this. Anopheles larvfie are often found in l)ools, rivers, etc., where fish are abundant, and pup.Te and mature larvjie among" them. This is seen in open pools as well as in the g-rass-grown rivers. He also says tli.it tadpoles do not attack the larva^ even in captivity, and g-oes on to say that larva' of (\)leo])tera and dragon-Hies, oftrn found in numbers in water with abundant Ano])h- eles larv.TB, even in cai)tivitv do not seem to devour them. In ponds where there are larcredeafed water-])lants. mosquitoes frequently escape the attacks of fish, and numy more of their natural enemies, by holding" to tlie water-surface, es])(H'ially above partly subm(M\ued leaves. This is es])ecially the case Avith Anopheles larva', which remain (juite at the surface during the best part of their existence VIII Remedies Against Mosquitoes AFTER a number of years' experience in fig-liting mosquitoes, the present writer has come to the conclusion that there is no reason why any com- munity should submit to the mosquito plague. At lirst he only went so far as to state that there are many places where the source of the mosquito supply is circumscribed and limited, and easily handled, and that in such places, with a comparatively slight effort and small expense, mosquitoes could be controlled. As the work went on and as experiments were tried on a gradually increasing scale, it became more and more obvious that any neigh- borhood, if it cares to take the trouble and go to the ex- pense, may iilace its mosquito denizens hors du comhat. But Avitli mosquito work, just as with so many other pub- lic measures, what is everybody's business is nobody's business, and the result is that in many localities every- one submits to the mosquito evil. In some instances, in- dividual effort is all that is necessary ; in others, united action on the part of the residents of a given neighbor- liood or a given community is needed, and, as will be later shown, there are still other measures which should 167 ins MOSQUITOES be handled by still larger organizations — even by States. Mr. Matbeson's clever phrase, referred to in the intro- duction to this book, " There is no more reason why peo- ple should sutler from mosquitoes than that thej^ should sutler from smallpox," is not an over-statement ; and that the effort should be made when it promises success is so self-evident that it only requires a few enthusiastic and enlightened individuals in a community to convince everyone of the desirability of an organized effort. Setting aside the question of yelloAv fever, which oid^^ at intervals concerns even the States along the Gulf of Mexico, and is of vital and constant importance only in tropical regions, a mere passing thought shows the eco- nomic loss to a neighborhood in the jn-evalence of ma- laria. While the actual death-rate may not be high, the number of persons incapacitated for their full share of work is alwa3's great. Families suffer in one way or an- other, and the community, when the matter is considered in a broad way, is a great loser. Aside, too, from ma- laria, it is perfectly obvious that a mosquito-ridden neighborhood is not a desirable jilace of residence. The very fact of the abundance of mosquitoes keeps real estate values at a depressed point. I know of one case where a stretch of land near a large body of water af- forded many excellent cottage and villa sites, but mos- quitoes were so numerous that even domestic animals could not be ke]>t in a healthy condition, and the sole population consisted of a few smoke-dried fishermen and their dogs. In this locality, by enterprising work on the part of one man, who organized a comi)any for the pur- REMEDIES AGAINST MOSQUITOES 169 pose, the land was boug-lit, tlie mosquito-breeding places were practically abolished, summer residences were built, and the company realized many thousands of dollars in the course of two years. There are, within a hundred miles of New York City, for example, hundreds of beau- tifull}^ situated localities which are not utilized to their full possibilities largely on account of the prevalence of mosquitoes. There are many small towns which are un- desirable for summer residence on account of the abun- dance of mosquitoes, though in all other respects their qualifications for this purpose are perfect. Aside from the main questions of health and of the value of land, come the other subsidiary questions of com- fort, and of the unnecessary expense of screening- houses with the thoroughness necessary in many localities, which, when considered in bulk, become important. It seems then evident that it would be a positive economj^ for a community to spend, if necessary, even a large sum of money in attempting mosquito-extermination. In ver}^ many cases, however, a small sum will suffice, provided it is administered with intelligence. Dr. C. Fermi, after giving an account before the Medico- physical Society of the University of Sassari, March 23, 1900, of his efforts to free the town from mosquitoes, esti- mated the expense of freeing a town of 50,000 inhabitants at from $200 to $300. This sum seems extremely small, even with the low price of labor over there, but in the case of Sassari the mosquito-sui5j)ly was local, and the insects bred almost entirely in household tanks and water receptacles. It is with large marsh-areas or numerous 170 3I0SQVIT0ES ponds ill iiei^liljoriiii::: woods, and especially with the liig-h brackish sea-coast marshes, that the expense would be- come very great. The consideration of tln^ question of remedies may most conveniently be divided into the following;- main cate.ijfories : (1) llemedial work against tlie early stages ; (2) liemedial work ag-ainst the adults. llemedial Work Apfainst the Early Stages. In considering the (question of remedies against the early stages, Ave again find it most convenient to sub- divide the subject as follows : (1) The treatiiiciit of breeding-places with insecticides ; (2) The abolition of breeding-places by drainage, and (3) The introduction of natural enemies into lireeding-pools, which for any rea- son it may be undesirable to drain, or to treat with oil. Before undertaking work against the early stages of mos({uitoes in any given neighborhood, it becomes neces- sary to make a thorough survey of tlu^ immediate sui'- rouiidings, and to learn with great accuracy all of the places in wliicli mosquitoes are breeding or may breed. In the section entitled " Queer Places in which Mosqui- toes Breed " ((^hapter I.) an effort has been made to cover the ground rather thoroughly as an indication of what must be looked for. All accidcMital receptacles f(U' stand- ing water must be enipiied and must be kejtt (Mii])ti«^d ; waste ground in the vicinity must be thoroughly ex- amined, in order to find wh(>ther there are hollows in wliich rain-water accumulates or whether there are broken REMEDIES AGAINST MOSQUITOES 171 bottles, empt}- cans, or discarded vessels of any kind. About houses, the greatest care must be taken to examine every possible spot where still water may occur ; cisterns must be covered tightly, with, however, a sufficient aper- ture covered with wire gauze to admit of a plentiful aera- tion of the water ; rain-water barrels should be either covered or treated with kerosene. In the surrounding ground every permanent pool and every swamp-area should be charted and the method of treatment determined upon ; permanent pools not used for Avatering- stock should be treated with kerosene ; swamp-areas should be drained ; and small depressions should be filled with earth. All such work must be thorough and practically perfect, else it is hardly worth while to undertake it. The Use of Kerosene on Breeding Pools. As long ago as 1812, the writer of a Avork pul)lished in London, entitled, "Omniana or Hor?e Otiosiores," sug- g-ested that by pouring oil upon water the number of mosquitoes may be diminished. Delboeuf, in the Revue Scientifqiie, 1895, says that he used kerosene in this way fifty years before. H. E. Weed, in 1895, stated that in the French quarter of New Orleans it has been a common practice for many 3^ears to place kerosene in the water tanks to lessen the number of mosquitoes in a given locality. Suggestions as to the use of kerosene were made by Mrs. Aaron, and by Beutenmiiller, in the Lam- born Prize Essays, " Dragon-flies versus Mosquitoes " (D. Appleton & Co., 1890). In 18G7 the present writer used 172 MOSQUITOES kerosene in a waterinf^ troug-li at Ithaca, N. Y., and found that moscjuito hxrvse were killed by it, and in 1892 con- ducted an experiment ui)on a larger scale in the Catskill Mountains, indicating the quantity of kerosene necessary for a given water-surl'acc and showing that adult mosqui- toes are captured by a kerosene film ; that is to say, they alight on the surface of the water in an attemjit to de- posit eggs and are dostro^'ed by the kerosene before the eggs are laid. A full account of this last experiment was published in Insect Life, vol. ii., 1892, and, since it at- tracted considerable notice in newspapers, additional ex- periments by others upon a larger or smaller scale were speedily made. Mr. H. E. Weed rid the college campus of the Mississippi Agricultural College of mosquitoes by the treatment with kerosene of eleven large water-tanks. Dr. John 13. Smith recorded in Insect Life (vol. vi). suc- cess with this remedy in two cases on Long Island. Pro- fessor Y. L. Kellogg conducted a similar series of experi- ments upon the campus of Stanford University, California, in which cases post-holes filled with surface water were giving out large numbers of mosquitoes, but when a little kerosene was poured into each hole the mosquito plague was almost immediately alleviated. Rev. John D. Long, at Oak Island Beach, Long Island Sound, and Mr. W. R. Hopson, near Stratford, Conn., conducted large-scale ex- periments with good results. Mr. R. M. Reese, in Balti- more, treated open sewers Avitli kerosene with excellent results. A little later (1898), Mr. W. C Kerr, on Staten Island, did some large-scale kerosene work npon ponds and swamps, which resulted most satisfactorily. In 1897 REMEDIES AGAINST 31 OS QUI TOES 173 Mr. M. J. Wiglitman oiled brackisli marshes at an Atlantic coast resort for a radius of about half a mile, reducing- the mosquitoes to innoxious numbers for an entire sea- son. Dr. St. Georg-e Gray, of St. Lucia, British West Indies, used kerosene in his well and in Avater-jars in his yard with excellent result. All of this work was done before the malaria discover- ies directed the attention of European observers especi- ally to the question of mosquito control. In the early work of the Italian investigators the use of kerosene was rather discredited, one of the reasons adduced being that although kerosene is abundant and cheap in America, it was not known to the Italians that it was extensively used in this country — a pretty poor reason, but still, more or less effective over there. Even Major Eoss, the English expert, seemed at first rather skeptical as to the value of kerosene, but returned from his West African expedition fully convinced of its value (Giles, 1900, pp. 76, 77), and since that time the use of petroleum oils has g-radually become the standard treatment for mosquito-breeding pools. For example, Fermi and Lumbao, the Italian in- vestigators, think that one man, with one day's teaching, could rid a good-sized city very largely of mosquitoes by repeating ten to twelve times, through a summer of seven months, the application of petroleum to the breeding- places. Mr. W. J. Matheson, in the summer of 1900, attained very successful results by treating an area of several square miles on the north shore of Long Island with kerosene, combined with certain drainage work. The army regulations in Cuba provide for the treatment 174 ji()S(jrn'(^h'S of brccdins'-pl'ices witli kerosene, and the results are re- ported to liave been admirable. The eity of Winchester, Va., during- the summer of IDOO, was treated with kcrosme, under an ordinance of the eity council, with such j^ood results that in the spring- of lOUl the city council passed a further regulation providing- a penalty for the non treat- ment of breeding-places. This instance is one of such wide-spread interest that the ordinances of 1900 and 1901 are printed herewith, together with a letter received in October, 1900, from the mayor of the city. [Mrst Cirrnhir, luno. \ PREVENT THE MOSgUITO. The City Council has pjissed the fullowinji; Ordinance : 1. Be it ordained that on or before March 2o, 11)00, and at least once each month thereafter until November 1, 1900, each owner or occupier f water. The eggs are glued together in the shape of a pretty little boat ;nid left to float and hatch. They retain this " wiggler" condition for from live to fifteen days, remaining all the time in the water but changing their skins several times. REMEDIES AGAINST 3I0SQUIT0ES 177 After from five to fifteen days the larvae become pupae or "tum- blers," so called from their bobbing up and down or turning over in the water. After five to fifteen days of pupa-hood the skin opens at the back and the mosquito comes out. It dries its wings ai^d is then ready for business on dry land. The female is the business member of the house, and it is she who sings and sucks the whole night through. The natural food of the mosquito is vegetation, and with this the male contents himself. It is the female alone that develops a carnivorous appetite. The life of the mosquito is short, but from the later hatchings of the fall a great number live over winter in garrets, cellars, etc., for the cold does not kill them. In early spring the female begins to lay her eggs, and as she lays about 300 in each bunch, the rate of increase is prodigious. Hence the importance of anointing witli oil all pools of water. When the female comes to lay her eggs she will desist, and lay- ing them on some twig or leaf, they will perish. If she alights on the oil-anointed water she perishes and her eggs perish with her. If the eggs have been laid before the oil is put in the water and the insects are in either larva or pupa state when the oil is put in, it will destroy them. The most important time then to fight this insect is just at this season before they have multiplied, as they will do in a few weeks if left alone. Since, however, the mosquito goes on lay- ing and hatching until about November, it is nece.sf>a ry to fight it all the season through, perhaps several seasons through. 178 3i()S(jr/'roi':s [Letter from the M(n/nr.\ "\Vix(I1i:sti;k, \'a., Uctoliur .">, I'JOO. Dr. L. O. Howard, EntDHioloyical Bureau Acjrirnltaral Dep't, Washington, J). C. Dear Sir : I have for some time h;ul it in iiiiiid to write you an ac('(tunt of our war afj^aiust the luowiuitoes in this town ; thinking that iiiasniueh as we made tlie fijjcht alou}.? the line of your published suggestions you would be interested in learning the extent of our success. Until about ten years ago a nios(iuito in Winchester was as rare as a horse in Venice. About ten years ago, the increase in their numbers beg.an to be apparent, but it was not until five or six years ago that they became a positive annoyance. Their advent here was attributed to a line of parlor ears established as a night train on the B. & O. R. K. , running from Camden Station, Balti- more, in the summer-time. This may have added to the num- ber, for recent investigation has shown that the returning empty cattle cars, which stand for a time at the stock-yards in Balti- more, bring great numbers of mosciuitoes all along this mountain country wherever the trains run. My own opinion, however, is that we owe the great increase to the scanty original stock here, which was enabled vastly to multiply its numbers because of a new and much extended sys- tem of water-works, which led to the greatly increased use of bath-tubs and water-closets ; and having no system of sewerage, the excessive use and waste of water stands in luimerous cess- pools, which are the i>rolitic l>rretling-i>la('es of tlie mosquito. Then, too, there is a stream of water, arched over where the streets cross, which, after heavy rains and when the regular stream has subsided to its ordinary dinu-nsions, consists of a large number RE3IEDIES AGAINST MOSQUITOES 179 of still pools, which are fine lor the egg-hatching and larva and pupa raising by the mosquito. The arches over this stream I found last spring to have been the favorite hibernating places of the insect, and before they liad fully time to wake up and go to business, I had millions of them destroyed by sprinkling with coal tar. Last summer my attention Avas called to your suggestions about the use of oil, by my brother-in-law, Dr. R. W. Baker, of your city. At my request he called on you and procured some of the literature issued by you on the sul)ject. 1 determined that I would urge the people here to try the experiment. In October, 1899, tlie mayor having died, I was unexpectedly chosen in his place, and I then tliought of trying to make the matter one for municipal and methodical action. I therefore induced the Com- mon Council to pass an ordinance, a copy of wliich I enclose to you. My proposition was greeted by the papers and by the com- munity generally with much merriment, and I was the subject of some veiy sharp ridicule from the press at home and abroad. The ordinance, as you will see, was witliout penalty, and the course designed to be pursued by me was intended to be per- suasive and not coercive. Early in the spring (March) I dis- covered tlie mosquitoes buzzing out from a pile of plank when the snow was six inches deep, and the first reports of the police who undertook to anoint the run and all public pools, was that mill- ions of them were found adliering to the arches, and the oil-cans when brought out from use under the arclies and in the pools were covered with the dead insects. I issued to the people small leaflets, giving an account of the habits and gestation period of the mosquito, and urging the peo- ple to obey the ordinance and join me in a relentless fight against the insect. I also asked many persons to make ex[)eriments and report their success to me. 1 was soon overwhelmed with re- 180 MOSQUITOES ports and all of them of the most favorable eharaeter. One entirely reliable fj:entlemaii repDrtid to that within five minutes after he had aiiointeil a rain-l)arrel, seventy-five mos- quitoes (presumably females) eaiiie to the barrel and seventy- three of them perished, wliilc tlic otlicr three made haste to escape. In one ease, a lady reported to me that she took nearly a pint of the dead inseets from a hoj^shead tiie mornin;^' after putting the oil in it. These and rc[)orts like tlicni <,n-eatly encouraged my efforts, and soon the oil was in almost universal use and the town smelled like a Standard Oil tank. I continued from time to time to issue the leatlets, and followi'd them u[) with a police ins[)eetion. The result has l)een a wonderful success. Tfie plague, while by no means entirely abated, has been decreased to a marked degree. In many parts of the town, the nets used so constantly heretofore have lu'eii thrown away, and there are no mosquitoes at all. In other i)arts, while their numbers are lessened, they still continm* to be a nuisance. This difference is doubtless due to the neglect of some persons in the particular neighborhood to use the oil ; and also, no doidjt, to peculiar facilities affonled for mo.sciuito breeding in some i)arts of the town more than in others. I observed a decided increase in tlie number in the latter part of August and in the month of Sep- tember. Just now we are greatly increasing our efforts toward their destruction, so as, if possible, to destroy the croj) that would hibernate, and thus reduce tlic number of breeders to live over to spring. There can be no doul)t about the success of the scheme. All that is needetl is persistent, unremitting ai)pIication of the oil to all pools, sinks, water-clo.sets, old cisterns, etc. , etc. , and another season we ex pe<-t to have an ordinance witli a penalty attaciied and to enff)rce the oil anointing even more systematically than has been done this year. REMEDIES AGAINST MOSQUITOES 181 To your suggestions we are indebted for what promises to be complete relief from this pest, and for an exemption during the past summer to an extent that has added very much to the i^leas- ure and to the profit of living in this town. I thank you very much in my own name, and in that of all of our people, for the good that your wise and practical investigations have done. Yours very truly, R. T. Barton. [First Circuhir, 1901.] MOSQUITO CAMPAIGN OF 1901. The admirable results obtained during the last year from fight- ing the mosquitoes seem to assure us that one more campaign will end them for Winchestei*, and restore conditions existing a few years ago when this insect was unknown here. The present ordinance is more stringent than that of last year and provides a penalty for its disobedience. Still, it is only the very few who are driven by the fear of the latv. Its successful enforcement de- pends after all upon a cheerful compliance by the good and law- abiding citizens. I publish the ordinance now, for your informa- tion, calling especial attention to the fact that the use of the oil must begin on March loth ; nuich earlier than last ye:ir, as we learned from observation that we did not begin early enough then. The oil must be renewed at least every three weeks, and I suggest, so that it may not be overlooked , that the first and fif teenth days of each month be " oil days " in your calendar. I hope that it will not be necessary either to appoint an in- spector or to impose a penalty for disobedience of the ordi- nance. R. T. Barton, Mayor. 18-2 3lOSQriT()ES An Ordiniinoe to provide a iiiothod for tho dostriu'tioii and pre- vention of the nios(iuito in tlie city of Winchester. Be it ordained by the Common Council : 1. That on or before Marcli 15, 1901, and at least every three weeks thereafter, until November 15, 1!)01, there shall be depos- ited in every open {jool or sink, or all from which there is any open- iii^C or outlet, and upon the surface of every barrel or hogshead kept for collecting rain-water ; and upon every receptacle of any sort in which water is allowed to stand for as much as twenty- four hours on every lot in the city of Winchester ; and on every open pool of any sort in every street or s(|uan' and alonir the bed or course of the town run, in said city of Winchesti-r ; kero- sene oil, at the rate of one ounce for each fifteen scjuare feet, and a proportionate quantity for any less surface. 2. It shall be the duty of every owner or occupier of any house or lot in the city to make the deposits of oil as provided in This ordinance; and in the case of barrels, hogsheads, or other recep- tacle kept on the premises for the collection of rain-water, water shall be drawn from said receptacle by a spigot of wood or metal placed as near as convenient to the l)ottom of said recejjtacle. o. It shall be the duty of the police, under the instructions of tlic niayor, to see to the enforcement of this ordinance, and to supply persons uiuible to secure tlieni witli the nec<'ssary oil .ind spigots. 4. The mayor shall have authority, if in his judiriiicnt the oc- casion retjuires it, to appoint an inspector of pools. siid of this oil was $2.25 per barrel, l)ut that in March, 1901, the iirice had advanced and was $3 per barrel, including the barrel, f. o. b. Point Breeze, Philadelphia, or Bayonne, N. J., an allowance for the barrel to be made upon its return, the allowance, however, depending entirely upon the condi- tion of the barrel when received bv the Standard Oil REMEDIES AGAINST MOSQUITOES 185 Company. It thus appears that this is not a hij^h-priced oil, and very likely in case of large-scale community work it could be bought by the tank-car at a verj^ reasonable rate. Kerosene may be applied simply hy pouring it upon the surface of the water, when it will spread of itself, or be spread rapidly by light winds, or it may be spread through a spraying nozzle. A spraying method was used successfully on Staten Island by Mr. Kerr and his asso- ciates. The laborers employed were furnished with bucket-pumps and were able to throw the spray into ponds for a considerable distance from the shore. The use of a spraying nozzle, however, does not seem to me to be desirable. I watched the oiling of ponds by this method at a New Jersey town, where the work was being carried on under the auspices of a ladies' town-improve- ment association, in the early summer of 1900. The water treated was all in small woodland ponds and there was a great waste of kerosene. The spray was diffuse, and be- came scattered over the vegetation on the borders of the ponds, a large share of it being wasted in this way. On small iDonds the oil can be sprinkled to advantage out of an ordinary watering-pot with a rose nozzle, or, for that matter, pouring it out of a dipper or a cup will satisfac- torily treat a small pond of, say a hundred square feet of water surface. With larger ponds, a pump with a straight discharge nozzle may be used. The straight stream will sink and then rise and spread, until the whole surface of the pond can be covered without waste. The English observers advise mopping the petroleum upon the surface 186 MOSQUITOES of the water by means of cloths tied to the end of a long- stick and saturated with kerosene. The use of such a mop may be desirable, even where a straig-ht discharge lium[) has been used, in order to commingle two suiface- sheets of oil. Tlu^ question as to the frequency of application of kerosene is an important one. In my early experiments I found that the kerosene was effective for some days after the odor had disappeared and after the iridescent effect upon the surface of tlie water had ceased to be per- ceptiV)le to the eye. A sing-le application to a small pool was certainly effective from twelve to fifteen days. The persistence of the oil, however, will undoubtedly vary with the temperature and with the character of tlie pool — whether exposed to the direct rays of the sun or shaded by trees. It is, at all events, safe to say that it will be per- fectly effective under nearly all circumstances, for at least a week, and probably longer. That means that for a week no mosquito can alight upon the surface and succeed in depositing eggs, and that even if she could do so the larvjc hatching from such eggs Avould be kilhnl. There- fore we must calculate from the end of such an etVective period to the end of the growth of larval and pupal life, and just before this second period is reached the applica- tion ^should be renewed. Under the most favorable cir- cumstances it will take from seven to ten days for a mos- (jnito hirva to reacli full growth, and tlie i)upa to become ready to give out the adult. Therefore, to tlie kerosene week must be added at least a W(>ek of larval and ])upal growth, wliich Avould require a second application of kero- REMEDIES AGAINST 3I0SQUIT0ES 187 seue after from fifteen to twenty days, in order to render it impossible that any adidt mosquito can be developed. This period is too short, rather than too long, but it is ab- solutely safe, and in any given locality observations will indicate to what extent it may safely be lengthened. I am quite inclined to believe that, even in tropical regions, seventeen-day intervals will be perfectly safe, if the fuel oil referred to above is used. My own experiments were carried on with illuminating oil, and the fuel oil is more persistent. The first army orders issued in Cuba (Circular No. 8, Headquarters Department of Western Cuba, October 15, 1900) required the treatment of breeding-pools once a month. The second order (General Orders No. 6, Head- quarters Department of Cuba, December 21, 1900) re- quired the application of kerosene twice a month. The Winchester ordinance, it will be remembered, designates as the times of application once every three weeks, but the mayor suggests that the first and fifteenth days of each month be " oil days." As interesting records, the army circular and order are given ; [Circular No. S.'l Headquartkks I)p:partment of Western Cuba, QuKMADos, Octo])er 15, 1900. The following couiinunicittion from the (!hief Surgeon is pub- lished for tlie information and guidance of commanding officers in this depai'tment. The necessary action will be taken as there- in recommended. 188 M0;S(JL1T0ES CiiiKF Surgeon's Office, Headqiartehs Department of Western Cuba, QuEMADOS, Cuba, October 13, 1900. To the A(ljtittjilk.s, they beiii^ much larger than tin' first set of stalks that appear ou uiy land. When I consider the faet that the land on which this asi»aragiis was growing has pro- iluced large crops every year for twenty years, without fertilizers of any kind, and still produces better crops than my land, which has had 1000 worth of fertilizers to the acre applied to it during the hist twenty years, it convinces nie that this land, for garden purposes, surpasses any which I have ever examined. . . . We realize, in a measure, the great value of the material which nature has for ages been storing up for man's future use, if he be wise enough to avail himself of it." It has been too frequently thought that to throw up an em- bankment to keep out the waters, and to build sluices and gates to let the interior water out, were all that was requisite; and, under this mistaken view, many instances have occurred greatly to the loss of the persons interested, and to the prejudice of the whole subject. An eminent engineer has said of reclamation : " What at first sight seems a mere mud and water proposition really requires, for its proper economic development, the best prod- uct of the latest practice in several fields of engineering and other sciences. Although the method of reclamation is centuries old, it may now be worked out by the aid of much that is novel in methods of construction and operation. ' ' Successful reclamation requires a most careful consideration of all the conditions existing, which generally vary in some feat- ures at every point, and not the least of the tliiliculties to be met, and one which to-day accounts for many expensive failures, is tlu' ravages of the musk-rat, and yet even he can be circumvented with proper care. Unsuccessful reclamations can all be accounted for by the neglect of some important point. A partially drained marsh is, no doubt, in a worse sanitary condition — more pesti- ferous and pestilential— than if not drained at all, and for mo.st crops it is likewise a failure. Besides, the soils in all mar.shes are REMEDIES AGAINST MOSQUITOES 207 not suited to the raising of crops, and one reclaiming-failure, even on that account, seems to olfset many successful ones. Care must be had in allowing for the subsidence of the marsh, which occurs in more or less degree, depending upon the character of the soil. Usually, where the marsh-level is sufficiently above mean low tide, reclamation can be effected without the use of ar- tificial means to care for the inner water. The cost of maintaining effective reclamation is slight if thor- oughly done in the first instance, but otherwise, becomes expen- sive and discouraging, and there are many fields once successfully reclaimed but now overflowed, resulting from the attempt at sav- ing a few dollars per acre in the original work. While it may be argued as against reclamation that there is plenty of cheap land without spending good money to obtain more acreage, yet this is not the way to dispose of the fact that these marshes are the prolific breeding-ground of mosquitoes, and that mosquitoes — how many kinds is not ascertained — bear the germs of a disease that, in its great prevalency, does more to reduce the vigor, which is largely the capital, of a nation, than any other disease. Mr. Weeks's mention in this article of the crops that can be grown upon reclaimed swamp -lands reminds me that Professor Milton AVhitney, Chief of the Division of Soils of the United States Department of Ag-riculture, has told me that the value of drained salt marsh-lands is very great for meadow purposes, and that when well drained, so as to prevent any danger of seepage waters coming near the surface, they are valuable for truck crops, if situated within easy reach of markets. In the work which was done by the Richmond County Club of Dongan Hills, Staten Island, under the leader- 208 MOSQUITOES ship of Mr. W. ('. Kerr, of tlit^ tirm of Westin^lioiise, Church, Kerr A; Co., New York, to whioli we have several times referred, coiisideral)le drainage of fresh-water swamps above the seacoast bhiti's was carried on with great success and at a minimum of expense. This work, together with the use of kerosene upon larger pools, re- sulted in complete relief from the attacks of the fresh- water mos(putoes, which during tlu; early summer had always been numerous and ferocious, l)ut down the blurts below the Club there was a large area of s;dt-)iiarsh, and in the higher i)ortions of this marsh-land the brackish water-mosquito of the Atlantic coast {Ciilex sollicitans) breeds abundantly and puts in its appearance up to the end of July in numbers. An attempt by members of the club was maele to buy this land in order to dike and drain it, with the idea that it could subsequently be let to truck growers, access to New York markets being easy and profits for truck farming in that vicinity being great. In the attempt, however, they found a singular obstinacy on the part of the owners of this worthless land, and the attempt was, at least temporarily, abandoned. A successful eifort of this kind, however, has been re- corded by the writer in a previous publication. It comes from one of the editors of the Scientific Aiiicriaw, who writes as follows : In the town of Stratford, Conn., where I have resided for the past forty-five years, we have been greatly plagued by swarms of iii()S(niitoes, so great, in fact, that the "Stratford mosquito" be- came a well-known eharaeteri.stie of Stratft)rd. We have in the southern part of our town, bordering on the .sound, several acres REMEDIES AGAINST MOSQUITOES 209 of luar^ili-kind or meadow, which would become periodically overflowed with water in the summer and a tremendous breeding- ground for mosquitoes, and this plague to the town continued until about 1890-91, when a party from Bridgeport, Conn., pur- chased a large section of the meadows and began to protect them by a dike, both on the north and south ends, which shut out the water. In addition to this, numerous drain ditches were made which helped to carry the water away. The result of this work made the land perfectly dry and spongy, so that after a rain no pools collected on tlie surface of the meadow and the creation of the mosquitoes was prevented. The transformation was so re- markable that people outside the town would hardly believe that it had been effected, and a year or two later the town voted a special appropriation of ^3,000 to the party who undertook to build the dike and render the meadows mosquito-proof. It had also the effect of placing on the market a large tract of land ele- vated from the sound, for residences, and as many as twenty- five sunnuer residences have been built upon this land bordering on the sound, and the number is inci-easingeach year. They are free from mosquitoes, so that the operation shows the economy and the benefit that will result by using some means for eliminating the mosquito-breeding pools. As lias been pointed out on earlier pag-es, nearly all of our mosquitoes breed exclusively in fresh water, and none of tlio forms which inhabit the United States, so far as ascertained, will breed in sea-water. Therefore, under certain peculiar conditions, another remedy is indicated by this fact, namely, that near the seashore, by a certain amount of ditching', the Avater of ponds may be converted from fresh to salt. A rather large-scale operation of this kind was conducted a few years ago at Virginia Beach, 210 MOSQUITOES the well known seacoast resort directl}^ cast of Norfolk, Va. Behind the hotels at this place, in former days — the hotels tiiemselves fronted upon the beach — was a large fresh water lake, which, with its adjoining swamp, was a source of mosquito-supi)ly, and it was further feared (although this was before the mosquito-dissemination of malaria was proven) that it nuide the neighborhood mal- arious. Canals were cut, and the water of the lake Mas changed from a body of frcssh to a body of salt water. The lake is now supplied with salt water at daily high tides by an underground feeder. Crabs and small fish occur in the lake in numbers, and no mosquito larvje are to be found even in August, even in the swampy places at the lake border. The water itself is very salt to the taste, and samples which have be(>n tested at my re- quest ])y Mr. E. E. Ewell, a chemist, showed that the total chlorine contained in the samples, calculated as so- dium chloride, is equivalent to 22.88 grams of that salt per liter, or 1,336 grains per United States gallon, or 3.05 ounces (avoirdupois) per United States gallon. The chlor- ine contained in sea-water is equivalent to 31.15 grams of sodium chloride per liter. The sami)les from Virginia Beach, therefore, contained approximately two-thirds of the (piantity of salt usually i)resent in the sea-water. Even Avhere states or communities cannot be induced to take up the question of marsh drainage and diking, it is possible for pul)lic-spirited individuals of means to do work in this direction which will count. For example, it is planned by a company of wealthy n)en who have sum- mer honii'S on the north sliore of Long Island, in the liKMEDIES AGAINST MOSQUITOES 211 vicinity of Oyster Bay, Cold Spring- Harbor, Lloyd's Neck, and Center Island, to spend several thousand dollars in this kind of work during- the summer of 1901, with the sole view of reducing" the summer mosquitoes of that region. This is mentioned as an indication of what might be done at other points. Introduction of Fish into FishiiKj Ponds. It happens quite often that larger or smaller iionds will be found which for some reason or other are considered too valuable to drain, and which the owners will not per- mit to be treated with kerosene, and yet in which mos- quitoes breed abundantly. Such ponds will, as a rule, be found to be milldams, ice-ponds, or pools artificially con- structed with rock and cement bottoms for the purpose of watering stock. Into such ponds it becomes absolutely necessary to introduce fish that will destroy mosquito larvte, which will otherwise invariably be found to exist in them in great numbers. The subject of the appropriate fish to use for this pur- pose has been considered in Chapter YII., and to that chapter the reader is referred. Remedies Against Adult Mosquitoes. In regions where mosquitoes abound, all houses must, as a matter of course, be thoroughly screened, if a meas- urable degree of comfort is to be gained. The extreme importance of the careful screening of windows and doors 212 MOSQUITOES in nuilarious neif^liboiliooJs cannot be too strongly in- sisted upon, wherever there is any reason to suppose that any work which may have been carried on against breed- ing-phices may not liave been so thorough as to be effect- ive. If mosquitoes of the mahii-ial genus Anopheles once gain access to a house they will remain hidden behind curtains or somewhere upon the walls during- the day and at night Hy out about the rooms in their search for persons to bite. Home observers of tropical countries say that in uni)rotected houses, Anopheles will frequently fly out and hide outside during the day, returning to the houses at night, but by far the more usual method seems to be to stay indoors. In addition to this screening, it is recommended that in tropical countries all the indoor walls of houses should be painted white or whitewashed, in order that the dark bodies of the mosquitoes may plainly be seen and that they may easily be caught. However, when the walls are not white and when the insects are hidden behind hang- ings or behind old-fashioned beds or elsewhere, they may be driven out of their hiding-i)laces with smoke and will then settle on the window-panes in the hope of es- caping. To kill living mosquitoes in houses, Fermi and Lum- bao recommend chlorine gas. Pour into a dinner plate containing four or five spoonfuls of chloride of lime five to ten cubic centimetres of crude suli)huric acid. This liberates the chlorine gas, which kills the moscpiitoes. The same writers state that the vapors of chloral act rap- idly, killing them in a few seconds, though these vapors REMEDIES AGAINST MOSQUITOES 213 can be used only in rooms which are not inhabited, or in which the vapors can be permitted to remain for several hours. The burning- of pyrethrum powder in such a room, when done in a proper way, will also kill the mosqui- toes or, at least, stupefy them. The pyrethrum powder should be moistened somewhat and moulded into little cones, which are then dried in the oven. When one of these cones is is^nited at its summit l)y a match it will smoulder slowlj^, fillino- the room with smoke, which to most people is not unpleasant, and which smells much like the sticks of punk which boys use to light fire- crackers. This smoke seems to stifle the mosquitoes, which fall to the floor. Two or three of these cones burned in a room in an evening will give relief by stupe- fying the insects, but on a warm summer night they will not take the place of screens, since the windows must be closed in case of any movement of the air, otherwise the smoke is not effective. The use of tin cups or inverted can-covers, the shal- lower the better, nailed to the end of a stick and contain- ing a very small quantity of kerosene, is very prevalent in some parts of the country for catching mosquitoes resting on the ceiling. AVliere the ceiling is white, the mosqui- toes can readily be observed and the tin cup is pushed u]) under them. When they attempt to fly they are caught by the kerosene and killed. I have seen dozens of them caught in this way of an evening in a mosquito-infested house. The first time I ever saw the apjiaratus was about 1890, in a New Jersey town. When about to retire to my 214 MOSQUITOES bedroom at night one of these stick-cups was given to me with a description of how it was to be used. I was too sleepy to experiment, however, and went to bed. On wakening the next morning I thought of the experiment and tested it with great success. Eighteen mosquitoes were caught on the ceiling of the bedroom, but as every one of tlunn was full of IJood, I regretted that the use of the instrunKMit had come as an after-thought. Celli and Casagrandi state that the substance which they call Larja^ith III, which (if I am correct in suppos- ing it to be a misprint for " larvicide ") is dinitrocresol — a yellow aniline color — will when burned in small quan- tities, kill the adult mosquitoes, and that this method con- stitutes the most efficacious method of destroying them. TIk; (^hinese use pine or juniper sawdust, mixed with a small quantity of brimstone and an ounce of arsenic, run into slender bags in a dry state. Each bag is coiled like a snake and tied with thread. The outer end is lighted. Two coils are said to be sufficient for an ordinary room, and 100 coils sell for six cents. There have been many substances recommended for use upon the skin in order to discourage moscpiitoes. Camphor, rubbed upon the face and hands, or a few drops upon th<^ pillow at night, will keep away mosquitoes for a time, and this is also a well-known propert}' of oil of pennyroyal. The use of oil of peppermint, lemon juice, and vinegar have all l)een recommended for use as pro- tectors against mosquitoes, while oil of tar is also used in bad mosquito localities. Dr. John B. Smith writes that in the matter of i)r('ventives, in his experience noth- REMEDIES AGAINST 3I0SQIJIT0ES 215 ing- is equal to oil of citronella. He lias used this ou the seashore Avith great success for three summers, and has recommended it to guuners and others, who have re- ported good results. Mr. E. H. Gane, of the firm of Mc- Kesson cfe Robbins, of New York, informs me that the essential oils which he has found most effective in keep- ing away mosquitoes have been the oils of lavender, cit- ronella, and eucalyptus, in the order named. The sub- stance, however, which he has found to work Avith most perfect success is castor oil. He wrote under date of Oc- tober 3, 1900, " Of course the application of this oil in its natural state is almost as objectionable as the bite of the insect, but by dissolving it in alcohol and adding some kind of essential oil or perfume, a preparation can be made Avhicli is not objectionable to most people and is very effective as a i^reventive of mosquito bites. The formula which I have been using with great satisfaction is : Castor oil, 1 ounce ; alcohol, 1 ounce ; oil of lavender, 1 drachm. The solution should not contain less than fifty per cent, of the oil, to be satisfactory in all cases. E^icalyptus. In addition to the use of eucalyptus oil to keep mos- quitoes from biting, as mentioned in the previous para- graphs, the growth of eucalyptus trees is said by certain persons to drive mosquitoes away, and trees of the genus Eucalyptus have been especially recommended for plant- ing in malarial regions. In 1803, Mr. Alvah A. Eaton, of California, wrote that in portions of California whore the 210 MOSQUITOES blue g-um occurs no otlier remedy need l>e sou.ulit for. Further than that, he stated that no matter liow pk-ntitul the mosquitoes are, a few twigs or leaves laid on the pil- low at night will secure perfect immunity. The same year, Mr, W. A. Sanders, of California, wrote that he had planted eucalyptus trees nineteen years previously about his house and that i\\e\ had reached, some of them, a height of 140 feet. An irrigating ditch ran through the g)'()V(% but there was never a single mosquito larva in the ditch in the grove, although on both sides of the grove larviic were plentiful. In the g-rove, mosquitoes were never found, though outside they were plentiful. This seems very strong evidence, but there is also evidence to show that eucalyptus trees are not at allcflective. Dr. Alfredo Dugcs, the well known naturalist of Guanajuato, Mexico, wrote me on September 8, 1900 : " I have received your very interesting study of the mos(piitoes of the United States, and thank you greatly for it. At the end of the book you speak of the utility of eucalyptus for driving awaj' insects. I have had some experience with these trees. The fresh leaves placed upon the pillow Avill attract mosquitoes. Thinking that the mosfjuitoes loved this plant, I have ])laced i\\o branches farthci- away, but without result. I have burned the halves in my chainl)er, and the cui'sed beasts have n^sisted the smoke." Dr. Nuttall states that malaria still i)r('vails in certain local- ities outside of Rome, in sjjite of eu(alyi»tus jilantings. REMEDIES AGAINST MOSQUITOES 217 The Castor-oil Plant. A great deal was said in the newspapers during- the winter of 1900-01 about the phxnting of the castor-oil phxnt to prevent mosquitoes. These notes were all based upon a consular report from Captain E. H. Plumacher, United States Consul at Maracaibo, Venezuela. The dis- patch, which was taken from Consular Report No. 246, March, 1901, reads as follows : A simple remedy against mosquitoes has been employed in sev- eral places in South Africa, and is equallj' well-adapted to the temperate zone. It consists in planting the castor-oil plant (Rici- nus communis), or "Palma Christi," around the house and premises. In cold and temperate climates the castor-oil plant grows to a height of four or five feet; in these countries, it becomes a tall tree and is perennial. It seems that the smell of the plant is dis- agreeable to mosquitoes and other insects, and it is an acknowl- edged fact that where these plants grow, few mosquitoes will be found. My personal experience bears this out. My residence is sur- rounded by plantain and banana trees, and I have been much trouljled in the past by the great number of mosquitoes which gathered between the leaves. Following the example of old settlers in the country, I planted the castor-seeds, which grew up in i)rofusion, and there are now no mosquitoes to be found among the plaintain and banana trees, although I keep the ground Avell irrigated. By keeping the branches and the seeds of the plant in rooms, the mosquitoes are driven away from the latter. There are several varieties of the castor-oil plant. In this coun- 218 MOSQUITOES try there are two — one with brown nuts, and the other white in color, with a kernel tasting like the fresh almond. E. H. Plumachek, Consul. Mauacaibo, November 30, 11»00. (Copied from Consular Reports, No. 24G, March. 1!»01.) Persons familiar with this pLant, and who have had it j?rowingr in their gardens, tell me that althoug-h they have heard the idea advanced before, they arc convinced that there is nothin<;' in it, and that the growth of this plant does not drive aw^ay mosquitoes. Remedies for the Bites. As elsewhere pointed out, different persons differ g-reatly in the effects which the mosquito-poison produces. Some jiersons are scarcely troubled by the puncture, while others are quite severely poisoned. It has been my own experience that if I can only refrain from scratching after having been bitten, no swelling results, and the irri- tation soon disappears. Even a small degree of scratch- ing, however, such as the ruljbing of one's cuff, or coat- sleeve, or collar, increases the irritation and produces a swelling, and sometimes white spots. Household am- monia has been found by many persons to give relief, and others say that a single touch of alcohol stops the irrita- tion. Dr. E. O. Peck, of Morristown, N. J., lias written me that he has found glycerine a sovereign cure for the bites. Touch the bite with glycerine and in a few minutes tlie pain is gone. He says also that glycerine takes the pain from bee stings. Dr. Charles A. Nash, of New York REMEDIES AGAINST MOSQUITOES 219 City, has written me that whenever a mosquito bites him he rubs the spot and marks it with a lump of indigo. This, he says, instantly stops the irritation, no matter whether the application is made instantly, or after the lapse of a day or so. He stated that he has used it since 1878, and has a g-ood opportunity to test it, for he lives in a locality where mosquitoes are abundant. IX Hoii' to Collect (did Prexe)Tc j\foHqHltoes Iiiclnding- an Acconnt of How to Raise Mosquitoes aud Study the Early Stages. ADULT mosquitoes are very fracfile creatures. Tlie scales upon their bodies aud legs are easily rubbed off, and the antenna^, and especially the legs, break with the least handling-. Even in their ordinary course of life the scales rub off, and with certain species an adult which is two or three weeks old is quite different in ap- pearance from one which has just (Miieiged from the pu^ta. Practically, they can not be handh^d with the fingers, or their value as cabinet s])eciiu(>ns or as spi^ciniens for study is lost. With some forms there are important charac- ters in the arrangement of the scales on the thorax. AVith others the scales on the wing are of importance and if the front legs an^ accidentally broken off, an imjiortant character to which I have i-eferred in the systematic ])or- tion of this book as (>xistiug in the claws of the foi'c feet, is naturnlly uiiavailabl<\ In capturing them, therefore, they must not be handled, and I have found the most sat- isfactory method of capture to consist in simid}' ]>lacing a small, open-mouthed vial over the mos(piit<» while at 220 BOJV TO COLLECT BIOSQUITOES 221 rest. On the wing it cannot be caiiglit, even with a deli- cate net, withont rubbing- or leg-breaking. If a mosquito lights upon your hand, or upon a twig or a leaf, or upon a wall of a room, it is quite easy, especially if it be en- gaged in sucking blood, to cover it adroitly with the vial. It rises almost instantly, and the mouth of the vial is plugged with a plug of absorbent cotton. A drop of chloroform on the cotton will stuj^efy the specimen almost immediately and another drop will kill it. The specimen may be kept permanently in the vial and when studied, if the study goes no farther than an exami- nation of the coarser characters in an attempt to determine the species, it will often suffice gently to slide it out upon a sheet of white paper and examine it with a power- ful hand lens. With the one-quarter inch achromatic triplet lens made by diiferent firms I have found it pos- sible to distinguish all of the generic and specific char- acters, even down to the teeth of the tarsal claws. This, however, is difficult to persons who are not accustomed to the use of high-power hand lenses, and in such in- stances one must break off a tarsus and mount it upon a slide in glycerine or Canada balsam for examination under a compound microscope. It is not advisable to mount adult mosquitoes bodily on slides in any medium whatever. They should not be pre- served in alcohol or formalin, but should be kept dry in vials. Of course they will rattle around somewhat and there is danger that the legs and the antennae will be lost ; therefore, if they are moved from the vial after the col- lecting and killing, into pill boxes with cotton, they can 222 MOSQUITOES be ciiniocT safely or can be sent in the mails. Several of the pill boxes may be placed inside a tight tin or wooden box and mailed with perfect security. A collection of mosquitoes should, however, not be kept in this way, provided it is intended as a study collection. The method which I have adopted and which is the one customarily used for small insects that are not too small for hand-lens work, is the triang-ular-tag- method. Take a sheet of stifi' paper or very thin cardboard and cut a strip, say, five-sixteenths or three-eig'hths of an inch wide. Then from this strip, by slightly oblique cuts, cut a series of triangles that will be pointed at the tip and a little less than an eighth of an inch wide at the base. Through the base of the tag maj^ be run an insect pin and to the tip the mosquito should be glued, white or yellow shellac being the best medium for the gluing. The mosquito should be glued on its side, just behind one wing, so that its back is away from the pin. This enables one readily, by holding the point of the pin in his hand, to examine with a lens all legs, antennn: , jialpi, one side, and the back. The tag should be pushed up on the ]un until it is from two-thirds to three-quarters of the length of the pin away from the point. To the lower part of the pin should be attached a small label, giving date, exact locality, and name of the collector, and below this may be pinned another small label, bearing the name of the insect. Those who for some reason do not like the jiapor tri- angle method of mounting use very minute pins made by Miiller in Vienna and known as " minuten insektcn nii- IIOJV TO COLLECT MOSQUITOES 223 deln," which are sold by Queen & Co., Philadel^jhia, and other hirg-e dealers in such thing's. These pins are so small and delicate that they may be thrust through the thorax of the mosquito and into a little strip of cork, the cork strip itself being pinned upon one of the larger and longer insect pins. Some collectors, instead of using the chloroform meth- od of killing, prefer the cyanide bottle. The cyanide bottle is made by taking a wide-mouthed tiask, putting a small lump of cyanide of potassium at the bottom and covering it with a layer of liquid plaster of Paris, which, when allowed to set, makes a complete layer over and around the cyanide and prevents the water that comes from the deliquescence of the cyanide from injuring specimens that are i^laced in the vial, but which at the same time is sufficiently porous to permit the escape of the deadly cyanide fumes. Even with the layer of plas- ter of Paris, however, the cyanide bottle will sometimes become wet, so that a bit of blotting-paper may with advantage be inserted to cover the plaster of Paris, and to absorb the superfluous moisture. A mosquito capt- ured in one of these cyanide flasks or vials dies very quickly and is in good condition for dry mounting or for transfer to pill boxes. The cyanide bottle is preferably stoppered with a cork stopper, but rubber stoppers are also used. In collecting early stages of mosquitoes it is only nec- essary to have a supply of bottles, a little coffee-strainer with a handle, and a large reading-glass. Other appar- atus is cumbersome and imnecessary. I have a large 224 MUSQL'ITUES reading-gluss four inches in diiimctov, with u stron.sf han- d\v, which 1 tind very usei'ul in exaniiiiin<4' the surface of water-pools, especially for Anopheles larva-. The dip- strainer used is an ordinary cheap cotiee-straini-r which has been mounted upon a long- handle, so that one can reach out two or three feet from the shore and caj^ture larvae and i)upa\ Other larger strainers with a fine mesh arc sold at the hardware stores and may l)e purchased cheaply. In bringing- larvic and pup;e in from the tield, tt)o much jarring- about in a bottle may residt in their death by drowning. It is desirable, therefore, to put moss or water- weed in the bottle with a minimum of ■Welter, provided the insects are transferred to an aquarium or a still jar within a few hours. Nuttall, Cobbett, and Strangeways-Pigg, who have done a great deal of collecting of mosquito larviu in England, as shoAvn in one of their important papers, entitled " Studies in Ilelation to Malaria," i)ublished in the Jour- Hdl of Ilyii'tene, vol. i.. No. 1, January, l!)Ul, used as their collecting apparatus some wide-mouthed bottles of me- dium size with cork stoppers ; a white enamelled dipper which, when required, can be tied with a piece of twine to a long bamboo r(jd ; a small i^ipette with a rubber bulb and small vials containing dilute alcohol for tlu^ preser- vation of larv.e which they did not wish to kee}) alive. They travelled over England on their collecting" trii)S on bicycles. When the larvae or eggs were captured in the porcelain di[)pers they were removed with a pipette and put in bottles, which were half tilled with water, wrai)ped in cloths, and attached to the bicycle frame. They found HO IF TO COLLECT MOSQUITOES 225 that tliey could be transported for several hours without injury. They noted also that the large larvae did not withstand the shaking as well as the small ones, but that a sufficient number could always be brought back for studying iDurposes. On expeditions lasting a couple of days they took precaution to remove the corks occasion- ally to give the insects fresh air. White dippers were used, since they could more easily detect the eggs or larvae on the white background, and they found that only rarely could they detect the insects by direct inspection of the surface of the water. LarvjTe and pupto, when it is desirable to preserve them in these stages, and it is always desirable to keep a small set of each species, may be kept in vials of alcohol or di- lute formalin (5 to 10 percent.). When preserved in alco- hol they should be j^assed through different strengths, beginning with a weak mixture, in order that they may not shrivel ; or, what is still better, kill the larva) or pupae suddenly in a cyanide bottle, then bring the water nearly to the boiling point in a little porcelain dish over an alco- hol lamp and drop the insects in, leave them until the boiling point is just reached and then remove them. An immersion of only a few moments will suffice. Ordina- rily the larv.To will sink at once to the bottom of the water and very soon thereafter rise to the top. This rising is an indication that the specimen should be removed at once. The specimen may then be preserved in ordinary commercial alcohol and will retain perfectly its color and shape. This method is used successfully with the larvae of many insects. It is not necessary to mount either 220 MOSQUITOES larvjc or pupa> whole on slides. One of those preserved specimens can be put in a cell with alcohol or glycerine and studied under a low power with perfect ease, and the examination of minute details of its anatomy, external and internal, may readily be accomplished by dissection, and the parts dissected out mounted permanently^ on slides in any of the ordinary media. In rearing dilierent species of mosquitoes I have had perfect success in the use of large, cylindrical glass jars known as battery jars. They can be bought in almost any city and of various sizes. The size which I tind most convenient will hold about a gallon of water. A layer of sand an inch or two deep is placed in the bottom of the jar and a quart or more of water poured over it. After the sand has settled and the water has cleared, a bit of almost any small water-plant may be inserted to ad- vantage, provided moscpiitoi's of the genus Culex are be- ing reared. If the experiment is with Anopheles, how- ever, some fresh-water alga is introduced, such as Sjiirogyra, Mougeotia, (Edogonium, Cladophora, or ()s- cillaria — almost any green scum from stagnant water, in fact. Over the top of the jar is placed a piece of swiss, or other fine, translucent cloth, held down l)y a large rub- ber band. The eggs of Culex may be had with ease by exposing a bucket of water out of doors in a mosquito locality on almost any summer night. If the eg^ masses be trans- ferred from the luicket to the prepared breeding-jar the growth of the larva' can be watched and their transfor- mations can be observed with perfect ease. Occasional HOW TO COLLECT MOSQUITOES 227 specimens can be taken out and preserved, to illustrate variations of different stages of g-rowtli. Accurate notes can be kept as to temperature, periods of transformation, and so on. A series of dates, provided several jars are under observation, can be written from time to time upon a slip of paper, which may be pinned to the edge of the cloth-covering- of each jar. Where the eg\gs of Anopheles, for example, have not been found, females collected at large may be liberated in such a prepared breeding-jar. They will rest on the under side of the cloth-covering during the day and at night will lay their eggs on the surface of the water. It is desirable to have a stick in the water, or a leaf, or a bit of cork, floating on the surface. I have had no difficulty in obtaining the eggs of Anopheles in large numbers in this way and the eggs of Culex as well, but although as many as fifty females of Psorophora have been liberated in breeding- jars i)repared in this way, I have not been able to get the eggs of this genus, which, as a matter of fact, are yet unknown. It is possible that Psorophora does not deposit its eggs upon the surface of water. This, however, is unlikely and it is rather to be supposed that the females used in my experiments were not old enough for oviposition and died from the confinement of the jar before the egg-laying period arrived. When one wishes to study closely the movements and intimate habits of the early stages of mosquitoes a great deal may be observed through the glass sides of the jar, by using a coarse lens and studying those near the edge. But when a closer study is desired, individual larvae or 228 MOSQriTOES pup;i^ may be liftt'J out with ta strainer and \n\i in a shal- low porcelain vessel where they can be watched witli ease under a dissecting- microscope. Anopheles larvae may be studied in this way very easily, anrl no nature study could be of more fascinating' interest than the observation of these creatures, lying as they do with the body practi- cally in a single plane, so that they may be easily watched, with the mouth-parts in constant action, and the head occasionally turning upside down and the re- verse with lightning-like rapidity. CHAPTER X Tlie Class'fjj eat 1071 of the TJnded States Mos- quitoes THE mosquitoes belong- to that order of insects known as the Diptera. The Diptera are the true flies. They possess but two wing-s, the second pair being- repre- sented only by two little projections known as halteres or poisers. The mouth-parts are formed for sucking and the transformations are complete, that is to say, the early stages differ radically from the adult. In the order Diptera the mosquitoes are separated into a distinct family known as the CulicidsB, the family name being derived from the name of the typical genus Culex (see Chapter III.), the generic name Culex being taken from the Latin word culex, which means a midge or a gnat. The true mos- quitoes of the family Culicidfe are distinguished by hav- ing the antennae furnished witli whorls of liairs, which are very delicate and long in the male, and sparse in the female. The head is furnished with a long, i^rojecting beak, which in the female is capable ot piercing the skin of human beings. The wings are as a rule transparent, but to the veins, when seen under the compound microscope, are attached scales of different shapes, something like 229 230 MOSQUITOES the scales of a butterfly's win£r. The Cnlieidne that occur in the United States arc divided into nine genera and about twenty-four recognized species. More species have been named, but some of them have been shown to be the same as others which were previously named, so tliej-- are included as synonyms. In the analytical tables which follow, the characters which distinguish these ditferent genera and s))ecies are given. These tabh^s have been drawn up by Mr. D. W. Coquillett, a well-known writer Fio. 48.— Claws of Front Feet of Culex siimvlans ; female at right, male at left greatly eiilari^^eil. (Original.) on insects of the order Diptera, who has made at my re- quest a study of the North American species of the family CulicidsTP. Tlie tables have been made as plain and as non-technical as jiossible, but there are a few points which sliouhl ])eiliaps be explained. In unrevised form, those tables apjteared in the writer's bulletin on mos(iuit<)(^s, published in August, 1900, and I have no- ticed that some ol)servers have found difliculty with the characters relating to the teeth of the tarsal claws CLASSIFICATION OF TJIE MOSQUITOES 231 and to the one which is mentioned as the " petiole of the first submarg-inal cell." In order to study the teeth of the claws of the front feet, it is necessary for most people to break off a foot and mount it on a microscope slide, for study with the compound microscope. One who is keen- sig'hted and expert with the hand lens can make them out pretty well with a rather high jiower (say a quarter-inch Tolles triplet) hand lens, but many others have great difti- FiG. 49.— Claws of Front Feet of Culex perturhans ; female at right, male at left ; grciitl}' enlarged. (Original.) culty in detecting them in this way. This, curiously enough, is especially true of those skilled in the use of the compound microscope. The terminal claws of the front feet of nearly all mosquitoes possess good characters in the teeth, and in order that readers may know just what to look for, the claws of the front feet of tAvo species are shown on the accompanying cuts, with the teeth plainly indicated. Whether a claw bears one tooth, or two, or none, is very important in the classification. 2:32 MOSijrrroKH CL Tlic expression " petiole of the iiist siil)m;ir<;iiiiil cell " is, I realize, incomprehensible to anyone not familiar with the vocalmlary of scientific entomoloo-y. Therefore on tlieaccompanyinsf cuts are indicated this first submarf^iual cell and its jiotiole. The j^etiole is the vein which runs from the end of the cell h.ick to the first cross-vein, and the relative length of this ]ietiole and of the cell it- self are of importance in the classification. The names nsed in this series of tal)les, an0. — Wing of Cnlex conso- hrinus (above) ; and C. pipicns (l)clow) ; showing petiole of first siihniiuginal cell; enlarged. (Original.) CLASSIFICATION OF THE MOSQUITOES 233 Yellow-fever Commission, and is of some importance to us, as Cuba is so near our Southern States, and American citizens have so many interests in Cuba. Another species of Megarliiniis, namely, grandiosa, Williston, has been added by Mr. Coquillett. It is unfortunate that this table has to be published be- fore the monographic work by Mr. F. V. Theobald, the Eng-lish expert, who has had exceptional advantag-es in his^studies, for the British Museum, of the mosquitoes of the whole world, makes its appearance. From correspond- ence with Mr. Theobald I learn that his opinions differ in some respects from those of Mr. Coquillett in reg-ard to the proper names for some of our mosquitoes. For example, the brownish, sordid mosquito which we called CuJcr. pungens is, in Mr. Theobald's opinion, composed of two distinct sjjecies, namely, Culex pipiens (a common Euro- pean mosquito), and Culex fatigans, an East Indian species which he saj^s is identical with Culex 2^11 n gens, and which he states occurs abundantly in many parts of the world, extending- north and south of the Equator to about 38'' north and south latitude (just about the rang-e of the yellow-fever mosquito). Mr. Theobald is also inclined to think that the Culex wipiger of Walker is identical with the species known to entomologists as Culex 71! gripes of Zetterstedt, and he also has a mosquito from North Amer- ica which he thinks is Culex cmnnlatus Meig-en, a form which we have not recog-nized in the United States. Mr. Theobald has also received from Canada an Anopheles which he thinks is a variety of A. hi/urcafus. This also is a species which is unknown to us in the United States. 234 MOSQCITOES It will bo noticed in the tables wliicli follow, Jiiid in the consideration of mosquitoes and yellow fever in Chapter V. that Mr. Coquillett and the writer have adopted the generic name Steg-oniyia for the mosquito which has in our previous writing-s been named (fulc.i'fasa'afia^. I have been induced to adopt this name throut^h correspondence with Mr. Theobald, who writes me that he has discovered characters M'liich separate this mosquito from the old g"enus C'ulex, and that he has ]iroposed the name Stej^fo- myia for the genus. He has given m(^ no clew as to the chai'acters upon which he has founded this genus, excei)t that they are " scale characters." A study of the scale structure of this insect and other mosquitoes of the genus Culex does not reveal any very important differences, but Mr. Coquillett, from other characters, has concluded to adopt Mr. Theobald's generic name, and it is here used with the characters pointed out in tlu; table. It will be unfortunate should this use of the name antedate the ]>ublication of Mr. Theobald's monograph, since the genus should be his and not ours. Two other new generic names pr()|)osed by Mr. Theobald, viz.: Toxorhyncliites and Con- chy Hastes, have been adopted and are characterized in the tables. It will be noticed that the characterizations are jn'inted with quotation marks, and that they are followed by ]Mr. Theobald's name in iinrenthesis. This method of printing Avill mak(^ Mr. Theobald res]ionsible for these genera as well as for Stegomyin, in the event that this book is issued from the ])ress in advance of his publica- tion. With these words of explMii.ition, the following tables, CLASSIFICATION OF THE MOSQUITOES 235 for which it must be distinctly iiiiderstood Mr. Coqnillett is responsible, and for which I owe him man}^ thanks, will probably enable those who are at all in earnest in the matter to distingnish our species without great difficulty. I. — Generic Synopsis. The following table contain^; all the genera of the long-beaked mosquitoes known to occur in North America. The males are readily I'ecognized by the aLntennse being densely covered with long hairs ; in the females the hairs of the antennjB are short and very sparse : 1. Palpi in the male at least nearly as long as the proboscis ; in the female less than one-half as long 3 Palpi in both .sexes at least almost as long as the proboscis . 3 Palpi in both sexes less than one-half as long as the pro- boscis 7 2. Proboscis straight or nearly so, colors of body brown and yel- lowish Anopheles. Prt)boseis very strongly curved, colors bluish or greenish. Meyarlnnus. 3. Legs bearing many nearly erect scales Psoiojihora. Legs destitute of such scales 4 4. Colors, black, Ijrown and yellowish, proboscis almost straight 5 '* Colors, green and bluish, proboscis very strongly curved " (Theobald) ToxorhyncMtes. 5. "Thorax marked with lines of silvery scales" (Theo- biild) Ste(jomyia. Thorax not marked in this way G 6. " Hind feet black, their apices .snow white'' (Theo- Ixild) Conchy I tastes. Hind feet not marked like this CnJe.v. 7. Upper side of thorax with line of bluish scales. . UranoUiuia. Upper side of thorax not marked in this way Aedes. 23G MOSQVITOES II. Genus URANOTiENiA. Our single species is rarely met w itli ; it is anions the smallest of mosquitoes ami will readily l)e recoj^ui/.eil by tiic strii)eof vio- let i)lue scales on tlie thorax : sdpiiJi'n'nid (). S. 111. Tjenus Ai<:i)KS. The sinjjle species is likewise rarely met with, and like the preceding;, is of very small size ; it is of a brownish color with fj^olden-yellow scales on the thorax and cross-bands of white ones on the alxlomen : funcus O. 8. IV. CtKXUS roNniYLTASTKS. Our two species are of medium size and of rather rare occur- rence ; they may be distinfi:uished as follows : With the last two joints of the hind feet white mnsicus Say. With oidy the last joint of the hind feet white. postU-ntus Wied. V. (tKM'S STKfidMYTA. Our two species are of rather small size, and may be distiu- fjjuished by the following characters : Front cl.Mws of the female toothed on the under side, the oilier silvery stripes of the thorax greatly widened in front of the wings. fiis Linne. Petiole one-fourth the length of that cell. . . pntigt^iis Wied. Petiole at least almost half the length of that cell. connobrtHUs Desv. {h) UNRECOGNIZED SPECIES. annnUiiun Schrank. This European species was credited to our fauna by Osten Sacken. ho.scii Desv. Probably a rubbed specimen of pniif/eiis. ni(jripes Zett. Black, the legs of the male dark yellow, hairs of pleura of female gray, a band of w'hite scales at base of each segment of her abdomen. rubidn.s Desv. The description was apparently founded on a rubbed specimen of P.soruphorti culf'ata. tentaceus v. d. Wulp. Must closely resemble ronsobiiitus. iiicidi'Hs Thomson. Is evidently a synonym of impiger Walker. higofi Hcllardi. According to the figure and description, the bands of black scales are at the bases of the al)dominal seg- ments; in the recognized species these l)ands are always at the apices of the segments. In other resi»ects this species must greatly resemble pnii'p'us. cubeusis Bigot. Apparently founded on a badly rubbed speci- men of puuyens. CLASSIFICATION OF THE MOSQUITOES 239 f rater Desv. This name was proposed for the Culex fasciatus of Wiedemann, under the impression that this is not the same species as the one described by Fabricius under the same name. It seems quite certain, however, that the word "proboscis" in Fa- bricius's description was simply a hxpsus for " palpi," and with this emendation the two descriptions agree very well. mexicanus Bellardi. Is evidently a synonym of jwsticatus. ptpiens Linne. A European species recently reported by Mr. Theobald as occurring in this country. provocans Walker. Is a synonym of nemorosus Meig. , accord- ing to Theobald. territans Walker. Is apparently related to jningens. Our recognized species of Culex and their synonyms may be listed as follows, the synonyms indented : consobri7ius Desv. ? annuUmanus v. d. Wulp (Anopheles). impatiens Walker. inornatus Williston. ping7ii's Walker. punctor Kirby. impiger Walker. inipldcabilis Walker. iiicidtns Thomson. ? quinquefasciatus Say. pertiirbans Walker. pipiens Linne. pungens Wied. ? boscii Desv. ? cubensis Bigot. "i fatigans Wied. stimulans Walker. tcEiiiorhynchus W ied. dainnosus Say. soUicUans Walker. tarsalis Coquillett. triseriatus Say. VII.— Genus Psorophora. Our single species is of a yellowish color, usually varied with brown, the bases of the tarsal joints white. It is considerably larger than any of our other species of yellowish or brown mos- quitoes : ciliatus Fabr. molestus Wied. ? rubidus Desv. 240 MOSQUITOES VIII. — a K\US TOXOKH YNCIIITKS. These are anions tlu' larjj^est of our iiiosciuitoi's, and closely re- semble those of the followhig {jjeiius. Our siiij^le .species has all of the feet marked with white : ratilus Coq. IX.— Gknus MK(iAiunxus. Our three species are aiuoiig the lar^^'st in this family, and are not known to occur north of tlie District of Columbia. They may be separated as follows : Hind feet alone marked with white 1 None of the feet marked with white hivmorrfioiddlis Fabr. 1. Front and middle feet wholly Idack. . . . portoriceiisi.s Roeder. Front and middle feet yellow, lirst joint of the front ones black * graudioaa Will. X. — GkXU.S AXOIMIKLES. (rt) UIX'OGMZKO hiPKCIES. 1. With a yellowish white spot near three-fourth.s the len;i:th of the front margin of the wing :} Without such a sjjot 2 2. Scales of last vein wholly I)lack, palpi wholly lilack fuacnlipcnn is MeifX- Scales of last vein white, marked with three black spots, palpi marked with white at bases of last four joints, criic/'dns- Wi«'d. 3. Hind feet wiiolly brown, scales of last vein white, those at each end black />niiittp( iiiii.s Say. Hind feet larj^ely siiow-whiti' on tlu' apical half. (/ r(/!/r/t(i rsi.s Desv. * This .species, of which I have never seen a specimeu, probably be- longs to the preceding genus. — 1). W. C. CLASSIFICATION OF THE MOSQUITOES 241 (6) UNKECOGNIZBD SPECIES. The following species which have been credited to our country have not been recognized with certainty ; some of them probably do not belong to the present genus, while a few were evidently founded on badly rubbed specimens in which the distinctive characters were therefore wanting : annulimanus v. d. Wulp. I strongly suspect that this does not belong to the present genus ; the description applies fairly well to the male of Ciilex consohrinus Desv. ferruginosus Wied. This name was proposed for the species previously described by Say under the name of Culex quinque- fasciatus, but the description differs so decidedly from the one published by Say as to give the impression that it is founded on a different species. I strongly suspect that the type of ferrugi- nosus is a rubbed example of Anopheles crucians, which was de- scribed from the same locality. Say's description of his Culex qui nquefasciatus agrees very well with the species which I have identified as Culex impiger Walker. macuUpennis Meigen. According to Theobald this European form is identical with our Anopheles quadrimaculatus Say. nigripes Staeger. This European species should be readily recognized by its unspotted wings. alhimantis Wied. Differs from our other species by the snow- white apices of the tarsi. pictus Loew. Is evidently closely related to crucians Wied. Our recognized species of Anopheles and their synonyms may therefore be listed as follows, the synonyms indented : argyritarsis Desv. maculipennis Meigen. crucians Wied. quadrimaculatus Say. ? ferruginosus Wied. punctipennis Say, hiemaUs Fitch.