List of Illustrations xi.
PAGE Diagram of the Nervous System ... ... ... ... ... 106 Generative Organs of a Gravid Female Mosquito ... ... ... 107 Sagittal Section of last Abdominal Segment of a $ Culex 109 Male Generative Organs of C.fatigans 110 Various Forms of Mosquito Eggs 123 Larvie and pupae of C.fatigans 128 Plate V. — Living J.TCqp7ieZes Larvae ... ... ... ... ... 128 Larva and Nymph of AnojjJieles ... ... ... ... ... 130 Caudal Extremity of Anopheles Bossii infested by a Parasitic Stalked Infusorian 150 Plate VL — Photographs of Living J.?iop /ieZes and CttZe.^! ... ... 139 Typical Garden Tank 194 View in an Indian cantonment ... ... ... ... ... ... 198 " Borrow pits '' beside an Indian Railway ... ... ... ... 198 Collections of Water in the Surface Drains of an Indian Cantonment 200 Levelling up the Site of an Actual Anopheles Tank 203 Railway Servant's Cottage in the Roman Campagna 227 Graphic Key to Generic Distinctions, based on Scale-characters ... 257 Plate VII. — To illustrate the differences between the sub-families, Anophelina and Culicina ; reproduced from the Jour, of the Bombay Nat. Hist. Soc 264 Typical Wing of Genns Meg arhina 266 To Illustrate the Genus Afe^ar/itnci 269 Wing of An. maculipalpis 3' (diagrammatic) ... ... ... 297 Wing of An. Pharcensis ? , Theob. var. alhofimhriatus, Giles ... 303 Anojjheles Lutzii ? ... ... ... ... ... ... ... 304 VJing oi An. leiocojjhyruSf'Domtz, J (diagrammatic) ... ... 312 Plates VIII., IX., X., XI. — Illustrating the Genera Anopheles and Cycloleppteron ... ... ,.. ... ... ... facing 332 Plate XII.— Illustrating the Genera Mucidus and Psorophora facing 346 Plate XIIL— Illustrating the Genera Janthinosoma, Panoplites, &nd TceniorliyncJius... ... ... ... ... ... facing 358 Plate XIV. — Illustrating the Genera Stegomyia and Armigeres facing 384 Venation of Wing in Culex ... . • ... ... ... ... 387 Plate XV. — CitZices with Spotted Wings facing 390 C. pipiens, Li., ajid C.fatigans, Wied., Contrsisted 440 Plates XVI., XVII. — Illustrating some other Culices ... ... 468 Deinokerides cancer, Theoh. J... ... ... ... ... ... 473 The Wing oi j3^doniyia veniistipes ... ... ... ... ... 479 Drawings to Illustrate the genus t/ra,n.oi«?i4«. ... ... ... 490 Wing oi Corethra Asiatica, sp. n. ... ... ... ... ... 507 Wing oi Mochlonyx velutinics, Biuthe ... ... ... ... ... 508 Figures illustrating recently described Anopheles and the New Genus Limatiis ... ... ... ... ... ... ... ... 509
LIST OF ABBEEVIATED QUOTATIONS.
The following quotations recui- so frequently that it appears more convenient to employ abbreviated references in their case, m place of citing them in full : — B. M. J British Medical Journal.
CM Angelo CeUi, "Malaria," translated by J. T. Eyre. London, 1900.
Desv. Essai Robineau Desvoidy, " Essai sur les Cuhcides, Mem. de la Soc. d'Hist. Nat. de Paris," III, p. 390, et seq. (1827). D. S " Diptera Saundersiana."
D. Sc Zetterstedt, "Diptera Scandinaca." F. A F. A. Schiner, "Diptera Austeriaca." Fab. E. S Fabricius, " Entomolog. Syst." IV. (1794). Fab. S. A Fabricius, " Syst. Antliat." IV. (1805). F. R Eugenio Ficalbi, "Revisions delle Specie Europei della Fagmilia deUe Zanzare," Bull. Soc. Ent. Ital. 1896, p. 239, et seq.
F. V. S Eugenio Ficalbi, " Venti Specie de Zanzare Italiane,' Bull. Soc. Ent. Ital. 1890.
G. S. Z "Studio di uno Zoologo, suUa Malaria." Memoria del Socio Baptista Grassi, R. Acad, dei Lmcei. Rome, 1900.
I. M. G Indian Medical Gazette.
J. T. M Journal of Tropical Medicine.
L. A Felix Lynch Arribalzaga, " Dipterologia Argentma," I, p. 345, et seq. " Revista del museo de la Plata" (1891). Macqt. D. E Macquart, " Diptera Exotica," I (1838). Macqt. H. D Macquart, "Hist, des Dipteres," S. a Buff. I (1834). Meig. S. B Meigen, " Syst. Beschreib. Europ. Zweifl. ins." Thl. VI (1830).
Memert Fr. Meinert, "De Eucephale Myggelarver." Vidensk. Selsk. 6. " Raekke, Natiirvidensk. Og. Mathem Afd." Ill, 4 (1886).
R. S.,M. C Reports to the Malaria Committee of the Royal Society. London : Harrison and Sons, 1900. S. A. C Skuse, " Monog. Aust. Culicidae," Proc. Lin. Soc. N.S.W. (1877).
Walker, List List of the Diptera m the British Museum, I (1848). Wied. A. Z. I. ...Wiedemann, " Aussereurop. Zweipflug. Insec." (1828). Wied.D. E Wiedemann, "Diptera Exotica," I (1821).
HANDBOOK GNATS OR MOSQUITOES PART I— GENERAL.
CHAPTER I.
On the Position and Terminology of the Culicidae. Without entering into minute detail, it may be well to premise that the Gulicidce belong to the Order of Diptera, or two-winged insects, in which the hinder of the two pairs of wings of the typical insect are absent as such, and are represented only by a pair of small club-like bodies, the halteres or balancers. All the members of this Order undergo a complete metamorphosis, i.e., they are hatched as worm-like larvce, and after attaining, as to size, if not as to form, the dimensions of the adult insect, and undergoing several changes of skin, they cease to eat, undergo profound anatomical changes, and become nymphs or pupce, and, finally, by a last change of skin, they emerge from the pupa case as the externally entirely different imago, or adult insect.
The Diptera are divided into two Sub-orders, the Orthorrhapha and the Cyclorrhapha, according to the method by which the pupse escape from the larval skin. In the former, the rupture is in the form of a T-shaped rent, and the larva is " encephalous," i.e., has a more or less perfectly developed chitinous head ; in the latter, the pupae escape by a circular opening and the larva has no definitely separated anterior division of the body, formed by the blended cephalic somites, 1
2 GNATS OR MOSQUITOES — CHAPTER I and the appendages and jaws are so little specialised, that it is commonly spoken of as being acephalous. It is obvious that this division, though associated with fundamental structural differences, is of little value to the observer who possesses only the perfect insect, but none of the Cyclorrhapha are at all likely to be confused with Mosquitoes, and the sub-divisions of the Orthorrhapha are marked by characters of a very obvious sort in the adult insect ; the Sub-order being divided in a very natural manner, into two sub-divisions, by the characters of the antennae. In the Nematocera, to which the Culicidce belong, the antennae are large and prominent organs, consisting of more than six joints, and the palp of four or five joints, while in the Brachycera the antennae are of insignificant dimensions, consisting of but two or three apparent joints, and the palpi are also but one or two jointed, Osten-Sacken further sub-divides the Nematocera into the true and the anomalous groups of families. The true Nematocera, which mclude the Cecidomyida, Mycetophilidce, Culicidce, Chironomidce, TipuUdcB, PsychodidcB, and possibly the Dixidce, have the following characters : — (1) The eyes are never blended into a single mass, and there is little or no difference in the size of the head and eyes in the two sexes.
(2) Eyes round, oval or lunate; they may meet but never blend.
(3) Antennae very large in proportion to the small head. (4) Legs long and weak, not fitted for walking. (5) Generally slighter, and more slender. (6) Inhabit damp, shady places, and prefer twilight. The anomalous Nematocera, which include the Simtdidcs or sand-flies, the Bihionida, dc, on the other hand, are characterised as follows : — (1) Head generally holoptic in both sexes, nearly always so in the male.
(2) Eyes often bisected, the upper facets being the largest.
(3) Legs well adapted for walking and often thick. (4) The sexes generally differ considerably.
POSITION AND TERMINOLOGY OF THE CULICID^ 8 (5) Have a peculiar and often sporadic geographical distribution. ,_.
The Culicidm, or sfleas.) are now included in the anomalous Nematocera by the majority of authorities. Confining our attention to the true Nematocera, the Culicidm may, for practical purposes, be easily distinguished from the other families by two very obvious characters. The first of these is the possession of the long, suctorial proboscis, which differs markedly from the mouth parts of any insect likely to be confused with them ; and the second is that in all the veins of the wings are fringed with scales like those of butterflies and moths. It is true that the wings of certain genera, such as Molopheles and Bypha- Gophua have the veins of the wings scaly, but even in the former the scales are very elongated, while in the latter they are more of the character of hairs, and in both the general arrangement of the scales is of a shaggy and irregular character as compared with that of the CulicidcB, apart from which they present unmistakable differences in the venation of the wings.
The family that is most easily confused with the Giilicidce is the Chironomidce or midges, which not onh^ frequent very much the same situations, but in general form so closely resemble the gnats that they can scarcely be distinguished by the naked eye ; but this family has neither the long proboscis nor the scaly wing veins, and a moment's examination with a lens suffices to distinguish them. Those who wish to follow more closely the question of the classification of the Nematocera are recommended to consult Mr. F. V. Theobald's " Account of British Flies," which is not only very plainly written, but appears more up to date than most of the accessible works on the subject in the English language. Although as yet it is, unfortunately, not completed, it contains a most handy synopsis of the genera of the Order, and will, therefore, be most useful to anyone commencing the study of any group of Diptera, even in tropical regions, for it must be remembered that the Dipterous fauna of India, and most other tropical parts, remains to be written, so that a knowledge of the general
4 (^NATS OR MOSQUITOES — CHAPTER I principles of the classification can only be gained from European and American works.
Hitherto I have treated the terms Culicidce, Mosquitoes, and gnats as synonymous, and the present work is confined to the consideration of the GulicidcB alone, but it must not be supposed that every insect that bites and is annoying to man necessarily belongs to this family. As far as we at present are aware, however, it is the GulicidcB alone that are concerned in the transmission of malaria, and as this handbook is mainly intended for the use of those who may be working on this problem, it does not appear worth while to include the Siviulidce and other obnoxious insects that attack man in the same way.
The word Mosquito is a diminutive of the Spanish and Portuguese " mosco " fly. A variety of insects of the GulicidcB and other families are known under this name in various localities, the only common characteristic being the power of annoying man by their bites. It is not uncommon to see in the press, notices of the occurrence of " Mosquitoes" in England. When investigated by competent entomologists, the insects always turn out to be one of the common indigenous English gnats, generally G. pipieiis, L. ; and in point of fact this species has as good a claim as any other to the name, and is quite capable of inflicting as much annoyance as any other, the tropical species surpassing our English gnat rather in numbers and persistence than in their individual capability of annoyance. Something of the same sort may be noticed in the case of the common fly, which even where fairly common, rarely exhibits in England the same dire determination to sit on one's nose that it does in India and other hot climates, and which it will do, even in England, when the weather is sufficiently hot. In short, the question whether gnats will earn for themselves the dreaded title of Mosquito or not is rather a matter of temperature than locality, or in other words, it is only in hot weather that gnats show any strong tendency to attack human beings in place of being content with their more usual vegetable food. At any rate, no one species is in any way entitled to the name.
f- Pig. 1.
Photographs of living mosquitoes (C. impellens, profile ; in the middle ventral aspects of the same ; views. About twice natural size. Facep.4.
Walk.;. Above <? and '^? in and beneath 9 and S dorsal
POSITION AND TERMINOLOGY OF THE CULICID^E 5 Oil this point, Mr. F. V. Theobald remarks: "Much ditterence exists between the so-called Mosquitoes of various parts of the world. Some are true gnats, others sand-flies {SimulidcE), and yet others midges, or Ghironomidce, of the genus Ceratopogun, such as the American so-called ' greygnat.' American Mosquitoes belong to the genera Culex and Simulium ; that of Cuba,. according to Desvoidy, is a Culex, while in Brazil the Mosquito is a small Simulium, Fig. 2.— An Indian " Sand Fly," common in Naini Tal. x 15 Diams. a, The left half of the insect is shown denuded of its tomentum, so as to indicate more clearly the details of the venation of the wing ; b, antennse of the same, more highly magnified.
sharing the honour with a true gnat {Psorophora molestus), according to Pohl and Kollar. From the West Coast of Africa I have had several kinds of Mosquito sent, including one or two Ctdicidce, but some were midges. It will thus be seen that the term is no guide to the family of insects to which any given ' Mosquito ' belongs. In any case, they all belong to families which are found in greatest abundance in swampy places."
The term "sand fly" is, however, at least as loosely applied as the word Mosquito, so that it must not be