162 ILLINOIS ACADEMY OF SCIENCE 



— . Dorsal abdominal segments not entirely so colored 8 



7. Ocelli placed considerably below the supra-orbital line, in the 



narrowest part of the front ; first dorsal abdominal segment 

 usually black ; scutellum usually with yellow hairs 



auricomus Robt. 



— . Ocelli placed near the supra-orbital line, above the narrowest 

 part of the front ; first dorsal abdominal segment usually with 

 some yellow pubescence ; scutellum usually with a strong 

 mixture of black hairs pennsylvanicus DeGeer. 



8. First dorsal abdominal segment entirely hlSiCk. .terricola Kirby. 



— . First dorsal abdominal segment not so colored 9 



9. Both second and third dorsal abdominal segments ferruginous 10 

 — . Second and third dorsal abdominal segments not both 



ferruginous 11 



10. Ocelli just below the supra-orbital line ; occiput usually domi- 



nantly yellow ; black band between the bases of the wings 

 more or less indistinct ; fourth dorsal abdominal segment 



ferruginous rufocinctus Cress. 



— . Ocelli not below the supra-orbital line ; occiput usually 

 dominantly black ; black band between the bases of the wings 

 distinct and broad, with its posterior margin usually extend- 

 ing backward in the form of a V ; fourth dorsal abdominal 

 segment yellow teniarius Say. 



11. Last two dorsal al)dominal segments with black pubescence 



dominant ; corbicular fringes black rufocinctus Cress. 



— . Last two dorsal abdominal segments with a light ferruginous 

 pubescence dominant ; corbicular fringes with some 

 ferruginous hairs frigidus F. Sm. 



12. Second dorsal abdominal segment entirely black, impafiens Cress. 



— . Second dorsal abdominal segment not entirely black 13 



13. First dorsal abdominal segment yellow ; second segment, except 



for a basal middle tawny patch, black ; remaining segments 

 black ; ocelli placed well below the supra-orbital line 



separatus Cress. 



— . Dorsal abdominal segments not so colored ; in some species 



the ocelli not below the supra-orbital line 14 



14. First four dorsal abdominal segments yellow ; fifth and sixth 



segments black fervid us subsp. dorsalis Cress. 



— . Dorsal abdominal segments not so colored 15 



15. Yellow puliescence of the pleura not extending to the bases 



of the legs IG 



— . Yellow pubescence of the pleura, at least the meso-pleura, ex- 

 tending to the bases of the legs 18 



10. Malar space longer than its width at lower margin ; ocelli 

 placed well below the supra-orbital line ; first three dorsal 

 abdominal segments mostly yellow, the remaining segments 

 black nevadensis Cress. 



— . Malar space not longer than its width at lower margin ; ocelli 

 not placed below the supra-orbital line, or only slightly so ; 

 first three dorsal al)dominal segments not as above 17 



17. Ocelli placed near the supra-orbital line, above the narrowest 

 part of the vertex ; malar space about as long as its width at 

 lower margin ; first two dorsal abdominal segments usually 

 yellow, and the remaining segments black; size medium 

 (15-21mm. ) perplexus Cress. 



— . Ocelli placed just below the supra-orbital line ; malar space 

 shorter than its width at lower margin ; second and third 

 dorsal abdominal segments usually with some ferruginous 

 pubescence, but the second segment sometimes with a basal 

 median patch of yellow pubescence, the remainder of the 

 segment being black ; size small (14-16mm.) riifocinctus Cress. 



