HENRY J. FRANKLIN. 241 



has a sufficient number of species to make a consideration 

 of the arrangement of their descriptions necessary here. In 

 this group, most of the New World species can be easily and 

 naturally separated into several more or less distinct sub- 

 groups, as follows : 

 Subgroup 1. bimaculatus and impatiens. 



" 2. ternarius,hunHi,fernaldi, vosnesenskii,edwardsii,fnelano- 



pygus, sylvicola and gelidus. 



" 3. perplexus, varans, cockerelli, bolsteri, couperi a.ndi/rigidus. 



" 4. pleuralis, flavi/rons and centralis, 



" 5 . ambiguus, sitkensis, tnixtus and alboanalis. 



Distinctive Characters of the Genus Bombus. 

 Females of two kinds, queens and workers, with mandibles 

 either three or four (exceptionally five or six) toothed (figs. 

 34, 36 and 37); labrum quadrangular in outline (fig. 107); 

 abdomen, except apical segment, well covered with pile over 

 practically the entire upper surface ; ventral apical segment 

 without lateral elevations (fig. C); posterior tibiae with outer 

 surface flat or slightly concave, naked, smooth and shining, 

 fringed before and behind with long hairs forming a pollen 

 basket (fig. B); end of each posterior tibia bearing, on the 

 inner side, a transverse row of stout spines (fig. 12); each 

 posterior metatarsus with a prominent projection or spur at 

 the base on the posterior side (fig. J). Male with genitalia 

 having corneus volsellae and squamae, and with anterior mar- 

 gin of labrum straight or incurved (fig. 51). 



Part I— SPECIES NORTH OF MEXICO. 



Table for Separation of Queens of Bombus. 



1. Occiput of head bearing light or yellow pile, or with a very strong 



admixture of light or yellow hairs 2. 



Occiput of head black or with only a very slight admixture of yel- 

 low hairs 60. 



2. Hind femora and trochanters black 3. 



Hind femora with considerable light pile, or the hind trochanters 



with light pile 37. 



3. Hairs fringing corbiculse with a more or less distinctly ferruginous 



tinge 4. 



Hairs fringing corbiculse black 10. 



TRANS. AM. ENT. SOC, XXXVIII. (31) 



