202 NORTH AMERICAN DIPTERA. 



Man/inn/ cell closed, antennae ir/f/i or tritli/mt <i terminal style, nut. with 



terminal hrist/r. 



1. Front tibiae with a terminal, claw-like spur. . 2 

 Front tibiae not with such spur. . . 3 



2. Thorax projecting prominently in front (21, 41). Pseudorus. 

 Thorax not projecting prominently in front.* . Doryclus. 



3. Veins at distal ends of the discal and fourth posterior cells paral- 



lel or continuous in the same straight line. . 4 



Veins at distal ends of discal and fourth posterior cells very dis- 



tinctly angulated and not parallel. . . 7 



4. Third joint of antennae with a terminal style, in length greater 



than the first two together; eyes not or but slightly emarginated 



on the sides of the front, the front much wider above; scutellum 



without bristles, or with hairs; small species (42) . Atonia. 



Third antennal joint without terminal style. . 5 



5. Third joint of antennae at least three times as long as the first two 



together; rather large species. . , Aphestia. 



Third antennal joint not more than twice the length of the first 



two combined; small species. ... 6 



6. First antennal joint more than twice the length of the second; front 



much widened above, the eyes disciform and with enlarged fa- 

 cets in front; scutellum with weak bristles ; body punctulate 

 (44). ........ Cerotainia. 



Third joint of antennae not more than twice the length of the sec- 

 ond; eyes on the sides of the front emarginate, the front not 

 widened above; scutellum with bristles; first posterior cell usu- 

 ally narrowed; body punctulate (22, 43). . Atomosia. 



7. Three submarginal cells present; first posterior cell closed or nar- 



rowed (23). ...... Pogonosoma. 



Two submarginal cells. ..... 8 



8. Antennae with a distinct terminal style. . 9 

 Antennae not with a terminal style. ... 10 



9. Rather small, nearly bare species, with pollinose spots or fasciae 



on the abdomen; first posterior cell open or closed (see Dasypo- 

 goninae, 16; Laphysha.} 



* The distinction between these two genera seems doubtful to me. 

 Megapoda is a distinct genus, characterized by the hind tibiae and 

 metatarsi not being thickened; the name is not preoccupied. 



