58 NORTH AMERICAN DIPTERA. 



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

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



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

 allel or continuous. . /. . - . . . . 8 



6. Third joint of the antennae 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 antennae without terminal style (> 



6. Third joint of the antennae 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 antennae 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. CKROTAINIA Schiner. 

 Third joint of the antennas 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. . . . . . 9 



First posterior 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 Rondani. 

 Two submarginal cells. . .10 



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



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



HYPKRKCHIA Schiner. 



Hind femora thickened toward the end; antennae without terminal 

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



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



tubercles below . . LAMPRIA Mat-quart. 



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



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



beyond the middle; proboscis thick. ." . DASYLLIS Loew. 

 Less pilose, more elongate species ; proboscis more elongate and slender. 



LAPHRIA Meigen. 



