160 ILLINOIS ACADEMY OP SCIENCE 



Key for the Separation of the Males of the Genus 

 Bremus from Illinois 



1. Eyes large and bulging out from the sides of the head; ocelli 



large and placed well below the supra-orbital line {Bremus, 



subgn, Bombias ) 2 



— . Eyes normal, not bulging out from the sides of the head ; ocelli 

 small, placed near the supra-orbital line, and above the nar- 

 rowest part of the vertex {Bremus) 6 



2. Third antennal segment as long as the fourth and fifth seg- 



ments taken together 3 



— . Third antennal segment not as long as the fourth and fifth 



segments taken together 4 



3. Sixth and seventh dorsal abdominal segments usually with 



ferruginous pubescence nevadensis Cress, 



— . Sixth and seventh dorsal abdominal segments black 



auricomus Robt. 



4. Second dorsal abdominal segment with its basal middle covered 



with a tawny or dirty yellow pubescence, the remainder of 



the segment being black separatus Cress. 



— . Second dorsal abdominal segment not so coloi-ed 5 



5. First two dorsal abdominal segments with yellow pubescence, 



the remaining segments black ; eyes greatly swollen and bulg- 

 ing out from the sides of the head ; malar space a mere 



line fraternus F. Sm. 



— . Last five dorsal abdominal segments usually with other than 

 black pubescence ; eyes somewhat swollen and bulging out 

 from the sides of the head ; malar space about one-half as 

 long as its width at lower margin or apex, .rufocinctus Cress. 



6. Fourth to seventh dorsal abdominal segments with black 



pubescence dominating 7 



— . Fourth to seventh dorsal abdominal segments not so colored ... 10 



7. First dorsal abdominal segment yellow, remaining segments 



black impatiens Cress. 



— . Dorsal abdominal segments not so colored 8 



8. First two dorsal abdominal segments entirely yellow 



Vagans F. Sm. 



— . First two dorsal abdominal segments not entirely yellow 9 



9. First dorsal abdominal segment, and at least the basal middle 



portion of the second segment, yellow bimaculatus Cress. 



— . First dorsal abdominal segment yellow ; second segment with 

 sides and apical margin yellow, the remainder having a 

 tawny or dull ferruginous pubescence afflnis Cress. 



10. First dorsal abdominal segment, except for a very few light 



colored hairs, black terricola Kirby. 



— . First dorsal abdominal segment not so colored 11 



11. Third dorsal abdominal segment black frigidus F. Sm. 



— . Third dorsal abdominal segment not so colored 12 



12. Second and third dorsal abdominal segments ferruginous 



ternarius Say. 



Second and third dorsal abdominal segments not so colored. . 13 



13. Dorsum of the thorax covered, except for a few occasional 



black hairs upon the disk, with yellow pubescence 14 



— . Dorsum of the thorax with more or less of a decided black 



band between the bases of the wings 15 



14. Third antennal segment as long as the fifth; occiput usually 



with yellow hairs dominating; malar space about as long as 

 its width at apex ; dorsal abdominal segments somewhat 

 variable, but usually with the first three segments yellow 

 and the remaining segments black perplexus Cress. 



