KEY TO THE BUMBLE-BEES. 



the supra-orbital line; yellow on second segment neither 



notched nor mixed with red; face and occiput black 



B. B. fraternus. 

 Otherwise, see B. affinis (8). 



11. First to fourth segments yellow, the remainder 

 largely black 12. 



Fourth segment black, also pleura and often the 

 scutellum 13- 



12. Pleura black; face and occiput largely light 



B. borealis. 



Pleura largely yellow; face (largely) and occiput 

 black B. fervidus. 



13. Ocelli large, separated, and below the supraorbital 

 line; first abdominal segment largely black, second largely 

 yellow, third yellow, the remainder black; occiput either 

 black or yellow; face black.' B. B. auricomus. 



Otherwise 14- 



14. Second and third abdominal segments yellow, the 

 remainder black except that there is often considerable 

 yellow on the fifth and sixth; face (largely) and occiput 

 black B. terricola. 



First (largely), second, and third abdominal segments 



yellow, otherwise black; face and occiput black 



B. pennsylvanicus (Plate XCIV). 



Males 



15. Ocelli large, the lateral ones not much, if any, more 

 than their diameter from the margins of the eyes, and 

 below the supraorbital line; eyes bulging 16. 



Ocelli otherwise 18. 



1 6. First (usually), second, and third abdominal seg- 

 ments yellow, the remainder largely black; sometimes 

 interalar black; third antennal segment as long as the 

 fourth and fifth combined B. B. auricomus. 



Otherwise colored and third antennal segment at 

 most not much longer than the fifth 17. 



17. First abdominal segment yellow, the remainder black 

 except for brownish on basal middle of the second and, 

 sometimes, yellow at sides of third; face largely yellow. 



B. B. separatus. 



451 



