399 

 Wirth and Stone: Diptera 



5 



with a curved horn and crested with a clump of fine 



bristles anips Dyar 



Subapical lobe of basistyle not divided, not bearing a 



leaf, dististyle not crested 3 



Mesosome lobes not bridged, broad and toothed apical ly 



apicalis Adams 



Mesosome lobes connected by a sclerotized bridge 



4 



Mesosome lobes broad apically but without teeth; dis- 

 tistyle strongly narrowed on apical 1/3... reevesi Wirth 

 Mesosome lobes toothed apically; dististyle narrowing 



rather gradually toward apex 5 



Mesosome lobes strongly narrowed and heavily sclero- 

 tized apically, bridge stout; dististyle membrane not 

 divided into lobes toward apex 



boharti Reeves and Brookman 



Mesosome lobes broad and not unusually sclerotized 

 apically, bridge narrow; dististyle membrane divided 



into lobes toward apex territans Walker 



Paraproct with basal arm at most weakly developed 



7 



Paraproct with a well-developed curving basal arm 



7. Median process of mesosome stout toward apex and 

 usually blunt or slanted apically, ventral cornu propor- 

 tionately smaller than in quinquefasciatus 



pipiens Linnaeus 



— Median process of mesosome slender toward apex, 

 pointed, straight, or curved near tip; ventral cornu very 

 large quinquefasciatus Say 



8. Median process of mesosome with several stout teeth 

 bordered by a group of close-set slender ones on inner 

 side of ventral cornu 9 



— Median process of mesosome not separated from ventral 

 cornu by a group of close-set slender teeth 10 



9. Subapical lobe of basistyle (starting basally) with 3 

 rods (basal one pointed), a short and slender hooked 

 spine, a leaf, and a long slender spine 



stigmatosoma Dyar 



— Subapical lobe of basistyle with 3 rods (basal one 

 blunt), no hooked spine, a leaf, and a slender spine 



thriambus Dyar 



10. Median process with about 5 teeth, 1 of which is very 

 long and slender, matching long external process; 

 subapical lobe of basistyle with 3 rods (basal 2 stout), 

 a spine (slightly hooked), a narrow leaf, and a slender 

 bristle tarsalis Coquillett 



— Median process without several teeth of which one is 

 long and matches external process; subapical lobe of 

 basistyle with 3 rods, slender and hooked club, broad 

 leaf, and bristle 11 



11. Median process of mesosome with 7 to 12 short and 

 stout teeth; external process large and very stout in 

 basal 3/4; basal process well developed, thumblike 



erythrothorax Dyar 



— Median process of mesosome with a single tooth sur- 

 passed by stout external process; basal process 

 weakly developed restuans Theobald 



Larvae 



Siphon hairs mostly single 2 



Siphon hairs double or multiple 3 



Antennal tuft inserted at apical 1/3 of shaft; lateral 

 abdominal hairs of segments 3 and 4 double 



thriambus Dyar 



Antennal tuft inserted slightly before middle of shaft; 

 lateral abdominal hairs of segments 3 and 4 single 



restuans Theobald 



Lower head hair with 3 or more branches, upper with 



4 or more branches 4 



Lower head hair single or double, upper single to 



triple 7 



Siphon with ventral tufts only tarsalis Coquillett 



Siphon with subapical tuft lateral or sublateral 5 



5. Dorsal microsetae toward apex of saddle conspicu'. 

 enlarged as compared with those at dorsal middle; 

 lateral hairs of abdominal segments 3 and 4 usually 

 triple stigmatosoma Dyar 



— Dorsal microsetae toward apex of saddle about as large 

 as those at middle; lateral hairs of abdominal segments 

 3 and 4 usually double 6 



6. Siphon tube 6-7 times as long as its basal diameter and 

 bearing 5 or 6 pairs of tufts erythrothorax Dyar 



— Siphon tube a little more than 4 (pipiens) to a little 

 less than 4 (quinquefasciatus) times as long as its 

 basal diameter and bearing 4 pairs of tufts 



pipiens Linnaeus 



quinquefasciatus Say 



7. Siphon with 2 dorsal tufts; lateral hair of anal segment 

 small and with more than 4 branches; upper head hair 

 short and double, lower long and single anips Dyar 



— Siphon without dorsal tufts; lateral hair of anal seg- 

 ment with fewer than 5 branches 8 



8. Siphon tube 7-9 imes as long as its basal diameter 

 which is about 2 times the apical diameter; upper head 

 hair double or triple, lower double or rarely single; 

 siphon tufts relatively short apicalis Adams 



— Siphon tube slightly to considerably less than 7 times 

 its basal diameter which is distinctly less than 2 times 

 the apical diameter; siphon tufts often 1/3 to 1/2 as 

 long as siphon 9 



9. Lower head hair double, upper triple reevesi Wirth 



— Lower head hair single, upper usually double 10 



10. Abdominal segment 4 much paler than 3 or 5; spicules 



near dorsal apex of saddle relatively slender; upper 



head hair double or rarely triple 



boharti Reeves and Brookman 



— Abdominal segments rather evenly pigmented; spicules 

 near dorsal apex of saddle becoming coarse; upper head 

 hair double or rarely single territans Walker 



REFERENCES 



AITKEN, T, H. G. 



1945. Studies in the Anopheline complex of western North 

 America. Univ. Calif. Publ. Entom., 7:273-364. 

 COOK, E. F. 



1956. The Nearctic Chaoborinae. Univ. Minn. Agric. Exp. 

 Sta., Tech. Bull. 218, pp. 1-102. 

 DEONIER, C. C. 



1943. Biology of the immature stages of the Clear Lake 

 gnat (Diptera, Culicidae). Ann. Ent. Soc. Amer., 36: 

 383-388. 



DYAR, H. G. 



1928. The mosquitoes of the Americas. Publ. Carnegie 

 Instn., 387:1-616. 

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



1924. The American Chaoborinae. Insec. Inscit. menst., 

 12:201-216. 

 FREEBORN, S. B., and R. M. BOHART 



1951. The mosquitoes of California. Bull. Calif. Insect. 

 Surv. 1:25-78. 

 HERMS, W. B. 



1937. The Clear Lake Gnat. Univ. Calif. Bull. 607, 22 pp. 

 MATHESON, R. 



1944. Handbook of the mosquitoes of North America, 2d 

 ed, 314 pp. 



PETERSON, A. 



1951. See Diptera references. 

 ROSS, EDWARD S., and H. RADCLYFFE ROBERTS 



1943. Mosquito Atlas, Part I. Ent. Soc. Amer., 44 pp. 

 YAMAGUTI, S., and W. J. LA CASSE 



1951. Mosquito fauna of North America, Parts I-V. 



Family DIXIDAE 



These small, delicate flies (fig. 14:18<z) are sometimes 

 included in the Culicidae, from which they differ in 



