58 NOKTII AMERICAN DIPTEKA. 



4. Veins at the distal end of the discal and fourth posterior cells parallel 



or continuous in the same straiglit line. ..... 5 



Veins at the distal end of the discal and fourth posterior cells not par- 

 allel or continuous. ......... 8 



5. Third joint of the antennas with a terminal style, in length greater 



than the first two together ; eyes not or but very slightly emarginate 

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

 without bristles, or with hair-like ones (West Indies and S. America.) 



Atonia Williston. 

 Third joint of antennw without terminal style (> 



6. Third joint of the antenna? at least three times as long as the first two 



together; large species (Central and South America). 



Aphestia Schiner. 

 Third antennal joint less than twice the length of the first two to- 

 gether. ........... 7 



7. First joint of the antennas about as long as the third; front much 



widened above, the eyes disciform and with enlarged facets in front ; 

 scutellum with weak bristles; body punctulate. Cerotaixia Schiner. 

 Third joint of the antennje longer than the first two together; eyes on , 

 the sides of the front emarginate, the front not widened above; scu- 

 tellum with bristles ; first posterior cell usually narrowed ; body 

 punctulate Atomosia Schiner. 



8. First posterior cell narrowed or closed. ..... 



First postertor cell wide open. . . . . . . .11 



9. Three submarginal cells present, i. e. the upper branch of the third 



vein is connected with the second vein by a cross-vein. 



Pogonosoma Kondani. 

 Two submarginal cells. 10 



10. Hind femora of nearly equal thickness throughout; antennai with a 



distinct terminal style; very large, robust, thickly pilose species. 



Hypereciua Schiner. 



Hind femora thickened toward the end ; anteiniaj without terminal 



style; more elongate, less pilose species. . . Nusa Walker. 



11. Thorax and abdomen nearly or quite bare; hind femora with spinous 



tubercles below Lampuia Macquart. 



Thorax and abdomen pilose ; larger species usually. ... 12 



12. Densely pilose species; the abdomen short, broad, usually broader 



beyond the middle; proboscis thick. . . Dasvllis Loew. 



Less pilose, more elongate species ; probo.scis more elongate and slender. 



Laphria Meigen. 



