420 AMERICAN HYMENOPTERA. 



Canadian provinces to the north of them. Is it present 

 in western Kansas and western Minnesota ? In California, 

 it probably is not to be found, except in the northern and 

 eastern portions of the state. What is its northern limit in 

 Canada and Alaska ? My most southern record is Mescalero, 

 New Mexico. It is mainly a Boreal and Transition form, 

 but it runs over somewhat into the Upper Austral Zone. 

 The species appears to be most abundant through the lati- 

 tude of Montana and Washington, where it is fairly common. 



The only close ally of this species, at least in the Western 

 Hemisphere, is B. auricomtis Robertson. The females of 

 that species can readily be separated from those of neva- 

 densis by their broad black interalar band and by their black 

 first dorsal abdominal segment. The males can be separated 

 structurally, as has been already shown, by differences in 

 the squamae of the genitalia and, furthermore, the apical dor- 

 sal segments of the abdomen of the auricomus male are 

 black. 



That the male known as improbus Cresson is the male of 

 nevadensis, I have the following proofs : 



1. Similarity of appearance . — These males look much more like the 

 queens of nevadensis than do any others known to me that have the 

 same habitat. 



2. Coordination of structure. — The females of nevadensis are very 

 closely related to those of auricomus , as shown both by structure and 

 appearance, and the ituprobus males are correspondingly closely re- 

 lated to the males of auricomus , as shown by their structure and ap- 

 pearance. 



3. Concordance of habitat. — These females and males have been 

 taken in the same portions of North America and in corresponding 

 abundance in the various regions. 



THE FRATERNUS GROUP. 

 Type. — Bombus iraternus Smith. This group is newly 

 established in this paper. 



Characters of the Group. 

 Females. — Labrum with tubercle-like areas widely sepa- 

 rated ; clypeus with anterior part of disc more or less smooth, 

 when punctate sparsely so and with rather coarse punctures. 



