189 



6. Wing veins without conspicuous scale-like hairs. .Dixidae (p. 279). 



— Wing veins with conspicuous scale-like hairs 7 



7. Wings short and broad, ovate, occasionally pointed apically ; tibiae 



without apical spurs; small, robust species with rather short 

 densely haired legs Psychodidae (p. 264) . 



— Wings elongate, narrow ; tibiae with apical spurs ; rather large, slen- 



der species, with long, slender, usually moderately hairy or scaly 

 legs Culicidae (p. 276). 



8. Wing with 2 to 4 distinct longitudinal veins 



Cecidomyiidae (p. 293) . 



— Wing with 5 or more longitudinal veins 9 



9. Wings with a secondary reticulation of fine creases or lines in addi- 



tion to the veins ; slender tipulid-like species with long slender 

 legs Blepharoceridae (p. 274). 



— Wings without a secondary reticulation of fine creases, at most with 



a longitudinal furcate crease between media and cubitus 10 



10. Abdomen in both sexes with a conspicuous flap-like scale at base of 



dorsal surface which is detached posteriorly and fringed with 

 long hairs Simuliidae (p. 302) . 



— Abdomen without such basal process 11 



11. Second basal cell of wing present 12 



— Second basal cell of wing absent 13 



12. Antenna consisting of 2 stout joints, and an apical arista-like one 



composed of 9 or 10 segments Orphnephilidae (p. 290). 



— Antenna composed of 10-11 joints, the apical portion stout, not dif- 



ferentiated arista-like Bibionidae (p. 298). 



13. Antenna consisting of 10-11 joints in both sexes (10 if scape is re- 



garded as consisting of 1 joint), the joints of central portion of 

 flagellum shorter than broad ; radius and costa conspicuous, the 

 other veins indistinct ; at least the mid and hind tibiae without 

 apical spurs Scatopsidae (p. 300) . 



— Without the above combination of characters 14 



14. Coxae unusually elongated 15 



— Coxae not unusually elongated 19 



15. Radius with 3 branches ; medio-cubital cross- vein present 16 



— Radius with only 2 branches, or if there are three present the medio- 



cubital cross-vein is absent Mycetophilidae (p. 248). 



16. Radio-medial cross-vein present, causing the base of the first poste- 



rior cell to be more or less broadly truncate 17 



— Radio-medial cross-vein apparently absent, fused with base of third 



branch of radius so that the base of first posterior cell is acute. 18 



17. Medio-cubital cross-vein much proximad of the radio-medial, caus- 



ing the posterior portion, divided longitudinally by media, to be 

 much shorter than the anterior portion . . Bolitophilidae (p. 247) . 



— Medio-cubital cross-vein almost directly in vertical line with the 



radio-medial, the 2 cells divided longitudinally by media subequal 

 in length Rhyphtdae, pt. (p. 241) . 



