80 american hymenoptera. 



Table for Determination of Males of Bombus South 

 OF THE Northern Boundary of Mexico. 



With only reddish-ferruginous, dark cinereous, or black pile (except 

 coccineus, which often has white pile on the apical dorsal 



abdominal segments 1 • 



With more or less pile of a color other than reddish-ferruginous, 

 dark cinereous, or black 13. 



1. At least the upper halves of the raesopleura clothed with orange 



or ferruginous pile 2. 



Mesopleura with no reddish or ferruginous pile 4. 



2. Malar space fully as long as its width at apex dalilbOMlii. 



Malar space much shorter than its width at apex 3. 



3. Dorsum of thorax cinereous haiidlirselii. 



Dorsum of thorax ferruginous riibicuiiclns. 



4. Abdomen with not more than one dark segment above 5. 



Abdomen with more than one dark segment above 7. 



5. Malar space considerably longer than its width at apex. 



caroliuus. 

 Malar space not longer than its width at apex ... 6. 



6. First dorsal abdominal segment black coccineus. 



First dorsal abdominal segment reddish or ferruginous baeri. 



7. Eyes swollen and bulging out from the sides of the head much 



more than those of the females; the ocelli placed far below 



the supra-orbital line brachycepbaliis. 



Eyes not swollen noticeably ; the ocelli near the supra-orbital 

 line 8. 



8. Dorsum of thorax black 9- 



Dorsum of thorax dark reddish-ferruginous eniiliJe. 



9. Apical dorsal segments of abdomen with little or no reddish-ferru- 



ginous pile 10 • 



Apical dorsal segments of abdomen with much reddish-ferruginous 

 pile dolichocepbaliis. 



10. Third antennal segment longer than the fourth solus. 



Third antennal segment at most not quite as long as the fourth. .11. 



11. Volsellae of genitalia extending considerably beyond the tips of the 



squamse 12. 



Volsellae not extending far beyond the tips of the squamae. 



atratus. 



12. Volsellae of genitalia with three nearly equal lobes at the end. 



kohli. 

 Volsellae of genitalia with two apical lobes each, these lobes dis- 

 tinctly smaller than the prominent rounded projection on 

 the inner side pullatlis. 



13. Eyes swollen more or less ; ocelli placed considerably below the 



supra-orbital line, the lateral ones very much nearer to the 

 eye margins than to each other 14. 



