110 NORTH AMERICAN niPTERA. 



notum bristly on the hind part only ; propleural and sternopleural bristles 

 absent; female abdomen with five segments; ovipositor flattened; first 

 longitudinal vein bristly. 



1. The picture of the wings consist chiefly of a dark border along the costa, 



from the base of the stigma to the tip of the wing, with the first 

 basal cell and the posterior cross- vein clouded; anterior cross- vein 



oblique. . . . . " 



Flies not having the above characters. - . . . . . 2 



2. Posterior angle of the anal cell drawn out into a sharp point (Mexico). 



OsTPiACOctEi.iA Giglio-Tos. 

 Posterior angle of the anal cell rounded. . .... 8 



3. Picture of the wings dark, varied with transparent spots and bars. 4 

 Wings not so marked . 5 



4. Scutellum large, flat ; occiput but little swollen ; veins of wings straight 



and markedly divergent. . . . . AMPHICNEPHKS Loew. 



Scutellum smaller, not flattened; occiput much smaller; epistoma 



strongly projecting; third and fourth longitudinal veins nearly 



parallel, sinuous (Mexico and South America). PLATYSTOMA Meigen. 



5. The picture of the wings consists of four blackish cross-bands, of which 



the third is nearly perpendicular, and the fourth lies along the costa 

 at the apex of the wing; scutellum with four bristles. 



RIVELLIA Desvoidy. 

 Wings without bands; scutellum with two bristles; ant-like flies. 



MYRMKCOMVIA Desvoidy. 



(>. Posterior cross-vein prolonged beyond the fourth vein (Cuba). 



HIMEROESSA Loew. 

 Posterior cross- vein not prolonged. . . ... . . 7 



7. Fifth longitudinal vein bristly (Mexico). HKICINIELLA Giglio-Tos. 



Fifth longitudinal vein not bristly.* . STENOPTKRIXA Mac-quart. 



CEPHALIIV2B. 



Oral opening very large; clypeus and proboscis greatly developed; pro- 

 pleural bristle absent; sternopleural bristle present; sixth segment of the 

 abdomen in the female distinctly developed ; ovipositor flattened; first 

 longitudinal vein bristly. 



1. Slender, Sepsis-like flies, resembling Myrmecomyia, with wings almost 

 hyaline, except for a small infuscation at the stigma and at the tip. 



CKI-HAI.IA Meigen. 

 Wings with a conspicuous picture. . ... . - 



* I can not see wherein Bridnnla Walker, to which Giglio-Tos refers a 

 Mexican species, differs from Stennjtteiina. 



