44 NORTH AMERICAN DIPTERA. 



2. Face projecting on each side in a rounded, conical protuberance, thickly 



covered with hair GLUTOPS Burgess. 



Face with two deep diverging furrows, running from the base of the 

 antenna? to the oral margin. . . . ARTHROCERAS Williston. 



LEPTIN^E. 



1. Front tibiae with terminal spurs. . 2 



Front tibia? without terminal spurs 3 



2. Front tibiae with a single spur ; sometimes only four posterior cells pres- 



ent in the wing. ., ", DIALYSIS Walker. 



Front tibiae with two spurs ; five posterior cells as usual. 



TRIPTOTRICHA Loew. 



3. Third joint of the antennae round, oval or pear-shaped, its bristle dis- 



tinctly terminal. . . . . . . . . . 4 



Third joint of the antenna? kidney-shaped, the arista more dorsal. 6 



4. Anal cell open ; hind tibia? with two spurs. . LEPTIS Fabricius. 

 Anal cell closed. 5 



5. Third joint of the antennae with a slender arcuate bristle ; hind tibia? 



with one spur. ..... CHRYSOPILA Mac-quart. 



Third antennal joint with a shorter, slender style. 



j SPANIA Meigen. 



( PTIOLINA Zetterstedt. 



6. Hind tibia? with two spurs ; anal cell closed. . ATHERIX Meigen. 

 Hind tibia? with a single spur; anal cell open. 



SYMPHOROMYIA Frauenfeld. 



14. STRATIOMYID.E. 



Small to moderately large, nearly bare or thinly pilose, bris- 

 tleless species. Head short, hemispherical or flattened, as 

 broad as the thorax. Ocelli present. Eyes contiguous or 

 separated by the front in the male. Antennae porrect, approx- 

 imated at the base, three-jointed, the third joint always com- 

 plex, usually with a terminal style or an arista. Proboscis 

 never elongated; palpi two or three-jointed, sometimes rudi- 

 mentary. Thorax never strongly convex; scutellum often 

 with tubercles, spines or projection on its margin. Abdomen 

 composed of from five to seven segments, usually flattened, 



