PAPERS ON ZOOLOGY 163 



18. First dorsal abdominal segment and a basal median patch of 

 the second segment yellow, remainder of the pubescence of 

 the abdomen black bimacniatus Cress. 



— . Dorsal abdominal segments not so colored 19 



lU. Malar space longer than its width at apex ; occiput usually 

 with yellow pubescence dominant ; sixth dorsal abdominal 

 segment always black vagans F. Sm. 



— . Malar space at the most not longer than its width at apex ; 

 occiput usually with dark pubescence dominating; sixth 

 dorsal abdominal segment sometimes rusty colored at its tip 

 affinis Cress. 



Key for the Separation of the Workers of the Genus 



B renins from Illinois 



1. Anterior dorsal portion of the thorax yellow ; a black band 



between the bases of the wings ; scutellum usually yellow, 

 but sometimes completely dominated by black pubescence.... 2 

 — . Dorsum of the thorax completely yellow, except for occasional 



black hairs aboiit the center of the disk 13 



2. Third, fourth, fifth and sixth dorsal abdominal segments with 



black pubescence 3 



^. Third, fourth, fifth and sixth dorsal abdominal segments not 



entirely black 5 



3. First dorsal abdominal segment with yellow pubescence ; 



second segment brown-ferruginous, except the sides and the 

 apical portions, which are yellow ; remaining segments mainly 



black affiu is Cress. 



— . Dorsal abdominal segments not so colored 4 



4. Occiput beai'ing black pubescence, or with only a few yellow 



hairs intermixed ; ocelli placed well below the supra-orbital 

 line : second dorsal abdominal segment entirely yellow ; 



medium to large size (13-22mm.) fraternus F. Sm. 



— . Occiput bearing mostly yellowish pubescence ; ocelli not well 

 below the supra-orbital line : second dorsal abdominal seg- 

 ment usually with side margins black; small size (7-14mm.) 

 rufocinctus Cress. 



5. First four dorsal abdominal segments entirely yellow ; fifth and 



sixth segments black H 



— . Dorsal abdominal segments not so colored 7 



6. Occiput and face with much light yellowish puliescence ; the 



middle anterior portion of the clypeus smooth and glossy 



iorealis Kirby. 



— . Occiput and face with black pubescence ; clypeus with its 

 middle anterior portion more or less punctate and as a rule 

 not glossy fcrvidiis Fabr. 



7. Second and third dorsal abdominal segments entirel.v yellow ; 



first segment yellow, black or both ; remaining segments black 8 

 — . Dorsal abdominal segments not entirely so colored 9 



8. Ocelli placed well below the supra-orbital line, in the narrowest 



part of the front ; first dorsal abdominal segment usually 

 black; scutellum iisually with yellow haim. .auricowus Robt. 

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

 part of the fi-ont : first dorsal abdominal segment usually 

 black, but often with yellow hairs ; scutellum usually with a 



strong mixture of black hairs pcnnsplvanirus DeGeer. 



0. First dorsal abdominal segment entirely black : apical segment 



whitish terricola Kirby. 



— . First dorsal segment not so colored 10 



10. Both second and third dorsal abdominal segments ferruginous 11 



