56 NORTH AMEKICAN DIPTKRA. 



17. All the tibia' and tlio hind femora with short, strong seta-. 



ECTHODOI'A LOC'W. 



Hind femora without sncli seta?. . . . Dioctp.ia .Meigen. 



18. Face distinctly swollen in profile, gibhose. . . . . .10 



J'ace flattened or gently convex. . . . . . . . "JO 



10. Thickly pilose species; the gibbosity of the face reaches to the base of 

 the antennas; anal cell usually open. . Cyrtoi-ogon Loew. 



Thinly pilose, more pollinose species, the convexity of the face con- 

 fined to the lower part; anal cell usually closed. Lasiopogon Loew. 



20. Abdomen elongate; front broad anteriorly, narrow behind. 



Pi-ESiOMMA Macquart. 

 Front not narrowed behind. ........ 21 



21. Hind tibia; toward the tii)r.nd the hind metatarsi nuich thickened. 22 

 Hind tibiie not, or but slightly, thickened toward the tip ; metatarsi not 



thickened. ........... 2o 



22. Head much brf)ader than high, transverse, "goggle-like"; abdomen 



short, wings large Holcocephala Jaeiniicke. 



Head only moderately broader than high, not at all spectacle-like in 

 appearance. ....... Holopogon Loew. 



23. Abdomen with thick, recumbent pile above; thickly ])ilose species; 



antennae slender Pycnopogon Loew. 



Abdomen without such pile above. ...... 24 



24. Slender, nearly bare species; face perpendicular, straight or gently 



concave, narrowed above and bare, except on oral margin. . 25 



Face gently rounded, not prominent below, in large ])art hairy and not 



or but slightly narrowed above. ...... 2(') 



25. Thickly whitish ])ollin()se; abdomen flattened, usually rt'flected up- 



ward ; third joint of antenna; and the style both slender. 



Stichop<)(;on Loew. 

 Less thickly pollinose; abdomen cylindrical, a little broader at the 

 base ; third joint of antenna' short and broad, the style minute. 



See Habropogon bilineatus Will. 



26. Large, elongate species, the style of antenna^ short. Calmnicus Loew. 

 Moderately large, and not much elongate species. ... 27 



27. Abdomen broader at the base, depressed; thorax much convex above; 



antennae slender, the style long and slender (compare also species of 



Cyrtopogon) Heteropogon Loew. 



Abdomen short, cylindrical ; lilack, with bright golden opaque pollin- 

 ose markings on thorax and abdonun. 



See Laparus pictitaksus Bigot. 



