SCENOPINIDAE OF THE WORLD 111 



10. Halter knob tan, posterior margin of 9th tergum toothed ventrally 



S. serratus, new species 



Halter knob yellow, posterior ventral tip of 9th tergum long with a single 



notch S. mirabilis Adams 



11. Wing brown or smoky brown 12 



Wing white or milky white 17 



12. Halter knob white 13 



Halter knob black-brown or red-brown 14 



13. Posterior margin of 9th tergum with a long dorsal point, parameres long, 



wiry S. cochisei, new species 



Posterior margin of 9th tergum with a ventral notch and point, parameres 

 long, wiry S. kuiteri (D. E. Hardy) 



14. Halter knob red-brown 15 



Halter knob brown to black S. valgus (D. E. Hardy) 



15. Abdomen with three white bands 16 



Abdomen with two white bands S. nubilipes Say 



16. Bands on abdomen relatively broad S. flandersi, new species 



Bands on abdomen narrow S. rossi, new species 



17. Halter knob white 18 



Halter knob brown, tan, or cream 24 



18. Abdomen with three white bands 19 



Abdomen with two white bands S. pecki, new species 



19. All white bands broad 20 



First band narrow, second and third wide . . . . S. alalacteus, new species 



20. Body without scales 21 



Body with flattened scales S. albifasciatus (D. E. Hardy) 



21. Small flies under 3 mm. ; veins separated at tip of wing 22 



Small flies over 3 mm.; veins R5 and Ml + 2 close at tip of wing 



S. cretatus, new species 



22. Small flies under 3 mm., but over 2 mm 23 



Small flies under 2 mm. long S. chico, new species 



23. Veins R5 and Ml + 2 widely separated at end of wing 



S. weemsi, new species 

 \'eins R5 and Ml +2 moderately separated=r-m cross vein 



S. vanduzeei, new .species 



24. Halter knob brown or red-brown 25 



Halter knob orange-yellow S. seftoni, new species 



25. Halter knob red-brown 26 



Halter knob orango-yellow S. seftoni, new species 



Halter knob brown, hind margin of the 9th tergum produced on the midpoint 



S. cooki, new species 



26. Third antennal segment short S. barberi, new species 



Third antennal segment long and narrow S. butleri, new species 



NEARCTIC SPECIES (FEMALES) 



1. Wing hyaline 2 



Wing brown or white 9 



2. Halter knob white 3 



Halter knob other color 4 



3. Lateral depressions on 8th tergum and sterniun . S. beameri (1). E. Hardy) 

 No lateral depression on 8th tergum S. whittakeri James 



4. Halter knob brown or red-brown 5 



Halter knob tan or yellow 8 



