FIELD BOOK OF INSECTS. 



First and second abdominal segments . yellow, the 

 remainder largely black ; face largely black . . B. B.fraternus. 



1 8. Second and third abdominal segments red; first 

 (largely) and fourth yellow ; fifth and sixth black ; interalar 

 black; pleura, face, and occiput, yellow B. ternarius. 



Third segment not red 19. 



19. Sixth and seventh abdominal segments largely red, 

 the others variable; face largely black; occiput yellow. . 



P. tricolor. 

 Sixth segment not largely red 20. 



20. First and fourth abdominal segments black; second 

 and third yellow; the remainder variable; interalar black; 

 pleura black; face largely yellow B. terricola. 



First abdominal segment largely yellow 21. 



21. First to fourth, inclusive, abdominal segments largely 

 yellow 22. 



Not so 23 (and also B. perplexus, 22). 



22. First abdominal segment usually with some black, 

 fifth usually black ; interalar, pleura usually, and scutellum 

 sometimes, black; occiput black; .6 to I in. long 



B. pennsylvanicus (Plate XCIV). 



No black on first or fifth abdominal segments; inter- 

 alar sometimes, and scutellum, yellow; interalar usually, 

 and occiput black; .4 to .7 in. long B. fervidus. 



No black on the first but usually on the fifth abdomi- 

 nal segments; interalar and usually the pleura black; 

 occiput and sometimes the pleura yellow. . . .B. borealis. 



No black on the first abdominal segment, but the 

 fourth and fifth usually black although the whole abdo- 

 men may be yellow; interalar, occiput, and usually the 

 face and pleura, yellow; face triangular, not long (as in 

 fervidus and borealis) B. perplexus. 



23. Second abdominal segment with little or no black. . 24. 

 This segment with considerable black 25. 



24. Occiput, interalar, and pleura, largely yellow; face 

 largely black ; first abdominal segment, usually the second, 

 and sometimes the third, yellow; abdomen otherwise 

 black P. laboriosus. 



Occiput (usually largely) and face black; interalar 

 often with much black;' pleura, and most of the first 

 abdominal segment, yellow; yellow of the second segment 



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