406 



Wirth and Stone: Diptera 



15. Ventral plate with a prolonged hyaline tip 



hunteri Malloch 



— Ventral plate not prolonged apically, unicolorous; 

 dististyle slender; basal tooth at extreme base, extend- 

 ing basad j . . jacumbae Dyar and Shannon 



16. Ventral plate more or less compressed, with denticles 

 on margin 17 



— Ventral plate broadly rounded without denticles on 

 margin meridionale Riley 



17. Ventral plate narrow, in the shape of an inverted Y, 

 with ventral process or keel arcticum Malloch 



— Ventral plate broader, tooth-shaped, without ventral 

 process venustum Say 



Pupae 



1. Respiratory organ consisting of a large ringed club 

 and 2 smooth, curved basal projections 



canadense Hearle 



— Respiratory organ consisting of slender branched or 

 unbranched filaments 2 



2. Respiratory filaments 4 3 



— Respiratory filaments more than 4 5 



3. Anterior margin of cocoon with a rather long median 

 projection latipes Meigen 



— Anterior margin of cocoon nearly or quite straight 

 4 



4. Dorsal respiratory filament strongly divergent from 

 other 3 aureum Fries 



— Dorsal respiratory filament not strongly divergent from 

 other 3 pugetense Dyar and Shannon 



5. Respiratory filaments 6 6 



— Respiratory filaments more than 6 7 



6. Filaments all arising rather close to base (front of 

 cocoon open ventrally with no transverse band below 

 opening) venustum Say 



tuberosum (Lundstroem) 



— At least 2 filaments arising at a considerable distance 

 from base trivittatum Malloch 



7. Front of cocoon with a basal collar at distinct angle 

 to surface so that the cocoon is boot-shaped (fig. 

 14:19p) 8 



— Front of cocoon with a narrow collar, little raised 

 above the surface, or the sides not touching antero- 

 ventrally, so the cocoon is wall-pocket-shaped 9 



8. Respiratory filaments 8, closely clumped' 



virgatum Coquillett 



— Respiratory filaments 12, more divergent (fig. 14:19A) 



arcticum Malloch 



9. Cocoon with a median projection from the anterior 

 margin piperi Dyar and Shannon 



— Cocoon with no long median projection from anterior 

 margin 10 



10. Respiratory filaments 8 bivittatum Malloch 



— Respiratory filaments 10 or more 11 



11. Respiratory filaments 10 argus Williston 



— Respiratory filaments 16 or more 12 



12. Respiratory filaments 16 vittatum Zetterstedt 



— Respiratory filaments more than 16 13 



13. Respiratory filaments 22-26 meridionale Riley 



— Respiratory organ of more than 100 fine filaments . . . 



hunteri Malloch 



The pupae of canonicolum, griseum, venator, and 

 jacumbae are not certainly known. 



REFERENCES 



CAMERON, A. C. 



1922. The morphology and biology of a Canadian cattle- 

 infesting black fly, Simulium simile Mall. (Diptera, 

 Simuliidae). Bull. Oanad. Dept. Agric, 5:3-26. 

 DYAR, H. G., and R. C. SHANNON 



1927. The North American two-winged flies of the family 

 Simuliidae. Proc. U.S. Nat. Mus. 69:1-54. 



FREEMAN, PAUL 



1950. The external genitalia of male Simuliidae. Ann.l 

 Trop. Med. Parasit., 44:146-152. 

 HEARLE, E. 



1932. The blackflies of British Columbia (Simuliidae, 

 Diptera). Proc. Ent. Soc. B.C., 29:5-19. 

 MALLOCH, J. R. 



1914. American black flies or buffalo gnats. U.S.D.A. 

 Bur. Ent. Tech. Ser., 26:1-70. 

 SMART, JOHN 



1944. The British Simuliidae, with keys to the species 



in the adult, pupal and larval stages. Freshwater Biol. 



Assoc. Brit. Empire, Sci. Bull. 9:1-57. 



STAINS, G. S., and G. F. KNOWLTON 



1943. A taxonomic and distributional study of Simuliidae 

 of western United States. Ann. Ent. Soc. Amer. 

 36:259-280. 

 STONE, A. 



1952. The Simuliidae of Alaska. Proc. Ent. Soc. Wash., 

 54:69-96. 



VARGAS, L., A. MARTINEZ PALACIOS, and A. DIAZ 

 NAJERA 



1946. Simulidos de Mexico. Rev. Inst. Salub. y Enferm. 

 Trop., 7:101-192, 25 pis. 



Family TENDIPEDIDAE (= CHIRONOMIDAE) 



The "midges" or "nonbiting midges" of the family 

 Tendipedidae form one of the most important single 

 groups in the ecology of aquatic environments. Midge 

 larvae are most abundant in the shallow water areas 

 of lakes, ponds, and streams favored by a heavy 

 growth of aquatic plants. However, in such areas 

 they are preyed upon more heavily by larger insects 

 and by fish so that more adult midges may actually 

 emerge from the deeper regions. Sandy bottoms are 

 also much less productive than soft mucky bottoms 

 on which most of the bottom-dwelling species are 

 dependent for building their tubes. Nearly all students 

 of fish food habits agree on the importance of midge 

 larvae, pupae, and adults in the diet of fresh water 

 fish (Townes, 1938); these stages are eaten by the 

 young of many species of fish and may be almost the 

 exclusive food of adult bass, trout, and whitefish. 

 The aquatic immature stages are also eaten by many 

 shore and water birds, especially those which are 

 bottom feeders. Although the adults cannot bite, they 

 may emerge in such numbers that they become distinct 

 pests around lake and stream-side resorts. 



Adult midges are readily distinguished by their 

 long antennae which are usually plumose in the males 

 (fig. 14:29t), shorter in the females (fig. 14:29/); by 

 the absence of a "V-suture" on the mesonotum, but by 

 the presence of a distinct median longitudinal furrow 

 or keel on the postscutellum (figs. 14 28a, k; 14:29t); 

 by the wing with the costa not continuing around the 

 wing margin past the wing tip, the media not forked, 

 but the mediocubitus forked at about the middle of the 

 wing; and by the reduced mouth parts. 



The larvae are distinguished by a complete head 

 capsule which is not retractable within the thorax; by 

 mandibles opposed; by anterior and posterior, often 

 long and slender, prolegs being nearly always present 

 (fig. 14:22/), on the prothorax and last abdominal 

 segment; and by the complete absence of functional 

 spiracles. The pupae are free, although sometimes 



