354 NORTH AMERICAN DIPTERA. 



TABLE OF GENERA. 



BY PROF. C. F. ADAMS. 



1. Proboscis elongate; slender, not retractile, usually as long or longer 



than the dorso-ventral diameter of the head. ... 2 

 Proboscis shorter than the head, thick and retractile. . . 15 



2. Proboscis slender and rigid, nearly or quite as long as the head and 



thorax together; labella small. ...... 3 



Proboscis as long as or but little longer than the head. . 8 



3. Scutellum and abdomen armed with spines. . Hystrisiphona. 

 Scutellum and abdomen with the usual macrochaetae. . . 4 



4. Sides of face bare. . . . . . . . . . 5 



Sides of face clothed with short bristles. . Prorhynchops. 



5. Palpi very short, thickened at tip; macroch&etae only marginal. 



Prosena. 



Palpi moderately long, not at all or but little thickened at tip; 

 macrochaetae usually discal and marginal. .... 6 



6. Claws of male extraordinarily long. i. . Mochlosoma. 

 Claws of both sexes short. ....... 7 



7. Facial carina broad, inflated, depressed. . . Myiomima. 

 Facial carina narrow, not inflated, compressed. Prosenoides. 



8. Abdomen densely covered with macrochaetae. ... 9 

 Abdomen with regularly arranged macrochaetae. . . . 10 



9. Vibrissae inserted some distance above oral margin (3, 4) . 



Hystricodexia. 

 Vibrissae inserted on oral margin. . . . Bathydexia. 



10. Eyes descending not more than two-thirds the distance to lateral 



oral margin. . . . * . . . . . .11 



Eyes descending at least three-fourths the distance to lateral 

 margin. . . . . . . . . . .14 



11. Fourth vein with a stump at its bend (1,2). . Scotiptera. 

 Fourth vein without stump at its bend. ..... 12 



12. Macrochseiae of abdomen cliscal and marginal. ... 13 

 Macrochaetae only marginal (12, 13) . . . Myiocera. 



13. Face quite concave in profile; vibrissae at oral margin. 



Myioscotiptera. 



Face nearly perpendicular; vibrissae some distance above oral mar- 

 gin (14, 15, 19.) ..... Rhynchodexia 



