10 U. S. NATIONAL MUSEUM BULLETIN 2 09 



in the Nearctic fauna, and is more in line with the narrower generic 

 concepts used in the rest of the tribes. A study of a larger portion of 

 the world fauna, however, ma}^ show a need for some different 

 groupings. 



Key to the Nearctic genera of Pepsini 



1. Mandible with three teeth (including the apical point as a tooth) ; dorsal edge 



of hind tibia smooth in both sexes; female with cardo of each maxilla giving 



rise to a fascicle of long curved hairs Dipogon (p. 115) 



Mandible with two teeth (a large apical point plus a smaller subapical internal 

 point; in a few species of Chirodamus from the Australian region there is a 

 more or less distinct third tooth) ; dorsal edge of hind tibia of female (and 

 often of male) with a serrate row of teeth (fig. 1, e) ; cardo of maxilla without 

 a fascicle of long hairs in either sex 2 



2. Second recurrent vein meeting the second cubital cell at about its apical 0.1 



(pi. 1, fig. 3); empodium about 0.75 as wide as the subapical width of the 

 last tarsal segment, its apical fringe of bristles containing about 14 to 40 

 bristles; first discoidal cell occupied basally by a distinct subcircular irregu- 

 larity in the membrane (pi. 1, fig. 3); large or very large species. 



Hemipepsis (p. 32) 

 Second recurrent vein meeting the second cubital cell at or basad of its apical 

 0.25; empodium about 0.5 as wide as the subapical width of the last tarsal 

 segment, its apical fringe of bristles containing about 8 to 10 bristles; first 

 discoidal cell not occupied basally bj^ an irregularity in the membrane, or if 

 so the irregularity less distinct than in Hemi-pe-psis 3 



3. Marginal cell separated apically from the costal margin of the wing, so that the 



tip of the cell is rounded (pi. 1, fig. 2) ; second cubital cell receiving the second 

 recurrent vein before its basal 0.33; large or very large species. 



Pepsis (p. 25) 



Marginal cell apically adjacent to the costal margin of the wing, so that the tip 



of the cell is pointed or subtruncate; second cubital cell receiving the second 



recurrent vein beyond its basal 0.4 4 



4. Second intercubital vein quite straight (pi. 1, fig. 1) ; legs and antenna short and 



stout, the second segment of flagellum in the Nearctic species 1.5 to 4.5 as 

 long as wide; clypeus (in the Nearctic species) wide, short, and rather flat; 

 brush on inner side of hind tibia broadly continuous to the apex. 



Chirodamus (p. 11) 

 Second intercubital vein usually more or less curved (straight in Priocnemioides 

 and in some Cryptocheilus) ; legs and antenna longer and more slender, the 

 second segment of flagellum rarely less than 3.2 as long as wide; clypeus 

 longer and more convex; brush on inner side of hind tibia often with a sub- 

 apical constriction or interruption 5 



5. Cubital vein not quite reaching the wing margin and the nervellus ending at 



or distad of the juncture of cubitella with discoideUa (pi. 1, fig. 4); clypeus 



very large Priocnessus (p. 40) 



Cubital vein usually reaching the wing margin, or if not (e. g., some species of 

 Priocnemis), then the nervellus ending distinctly basad of the juncture of 

 cubitella with discoidella 6 



6. Under side of last tarsal segment with two longitudinal rows of bristles; second 



intercubital vein straight or evenly curved 7 



Under side of last tarsal segment without any preapical bristles or with a very 

 few that are not arranged in two regular longitudinal rows; second inter- 

 cubital vein rather straight anteriorly, but strongly curved posteriorly . . 8 



