236 AMERICAN HYMENOPTERA. 



tween individuals of the same sex and species than are the 

 structural characters and it is, therefore, less reliable in the 

 determination of species. The coloration is much more con- 

 stant on some parts of the body than it is on others. The 

 following list is arranged to indicate, in a general way, the 

 relative coloration constancy of the different parts of the 

 body which present color characters much used in the classi- 

 fication of species in this paper. In this list, each part men- 

 tioned is, in the writer's opinion, usually more constant in its 

 coloration within sex, or caste, and species limits than is the 

 next following part : 



(a) . The hairy fringes on the front and hind borders of the hind 

 tibiae (the corbicular fringes of Bombus) . 



(b). The face and occiput of the head and the front part of the dor- 

 sum of the thorax. 



(c). The hind trochanters and femora. 



(d). The portion of the dorsum of the thorax between the bases of 

 the wings. 



(e). The mesopleura. 



(f). The scutellum. 



(g). The dorsum of the abdomen. Of this part, the apical portion 

 is, in very variable species, much more constant in its coloration than 

 are the middle and basal portions, and the basal portion is usually dis- 

 tinctly more constant than the middle portion. 



Melanism. 

 The writer has never seen or heard of a true albino bum- 

 ble-bee. Melanic specimens, however, though rare, are occa- 

 sionally found. The writer has seen three such specimens. 

 Two of them were queens of B. pennsylvanicus and the other 

 was a queen of B. auricornus. In all these specimens, the 

 pile that is usually yellow was very much darkened and 

 looked sooty, there being hardly a sufficiently strong trace 

 of the yellow to make identification possible. 



Freak Specimens. 

 Specimens having an aberrant coloration of pile are very 

 common. This, together with the very great normal varia- 

 tion of some of the species, has been the cause of the very 

 great confusion which has existed in the classification of the 



