112 U.S. NATIONAL MUSEUM BULLETIN 2 77 



5. Cell R5 tapering to edge of wing 6 



Cell R5 sharply constricted before the end of the cell 



S. gossypius, new species 



6. Legs with tibia red-brown 7 



Legs with tibia orange-brown to brown . . . . S. magdalenai, new species 



7. Eighth tergum flat with lateral depressions 



S. beameri fuscus (D. E. Hardy) 

 Eighth tergum rounded without depressions . . . . S. valgus (D. E. Hardy) 



8. Halter knob tan, tip of cell R5 sharply closed . . S. howdeni, new species 

 Halter knob yellow, tip of cell R5 open S. mirabilis Adams 



9. Wing brown or smoky brown 10 



Wing white or milky white 16 



10. Halter knob light 11 



Halter knob dark 13 



11. Halter knob cream or tan 12 



Halter knob white S. vanduzeei, new species 



12. Halter knob cream, antenna long, straight . . . . S. kuiterti (D. E. Hardy) 

 Halter knob tan, antenna short, pear-shaped. . . . S. cochisei, new species 



13. Cell R5 narrowed at edge of wing 14 



Cell R5 open at edge of wing 15 



14. Halter knob red-brown to black-brown polished . . . . S. nubilipes Say 

 Halter knob red-brown above white below S. hagai, new species 



15. Tarsi light red-brown S. bryanti, new species 



Tarsi straw yellow S. flandersi, new species 



16. Halter knob white 17 



Halter knob brown or tan 21 



17. Halter knob all white 18 



Halter knob with base tan S. weemsi, new species 



18. Body without flattened scales 19 



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



19. Third antennal segment not parallel-sided 20 



Third antennal segment uniform width S. chico, new species 



20. Third antennal segment oval, widest at middle . . S. alalacteus, new species 

 Third antennal segment pear-shaped, widest at base 



S. cretatus, new species 



21. Halter knob brown or red-brown 22 



Halter knob orange-yellow S. seftoni, new species 



22. Halter knob red-brown 23 



Halter knob brown above, white below S, pecki, new species 



23. Antenna black-brown elongate oval, frons swollen above antenna with a 



broad median depression on lower fourth S. rossi, new species 



Antenna red-brown, short, frons swollen above antenna with a median 

 groove dividing lower two-fifths S. barber!, new species 



NEOTROPICAL SPECIES 



1. Males 2 



Females 6 



2. Wing hyaline, abdomen with two or three white bands 3 



Wing milky white, two white bands on abdomen . . . S. pygmaeus Loew 



3. Halter knob brown or red-brown, abdomen with three white bands ... 4 

 Halter knob white, abdomen with two white bands (Hawaii) 



S. adventicius (D. E. Hardy) 



4. Halter knob red-brown, abdomen with some narrow white bands .... 5 



