HENRY J. FRANKLIN. 281 



sion that he was correct. The evidences of their relationship 

 are as follows : 



1. They have exactly the same range of habitat. 



2. No other queen Bombus in the eastern part of the United States 

 is without definitely and satisfactorily determined workers. 



3. No other Bombus workers and males in the eastern United States 

 are without a satisfactorily determined queen. 



4. The queens, workers and males, by their structures, are all easily 

 placed in the Terrestris group, of which there is no other eastern repre- 

 sentative, except B. terricola. 



THE BOREALIS GROUP. 



"The group of B. fervidtis'' Radoszkowski, Bull. Soc. 

 Natural. Moscow, xlix, P. 1, 1884. p. 77. 



Type. — Bombus borealis W. Kirby. The first of the three 

 species which Radoszkowski placed in this group was really 

 borealis, but he misidentified it as fervidus. 



Characters of the Group. 



Females. — Pile rather short and fine ; head elongate tri- 

 angular in outline ; mandibles as in Pratorum group ; malar 

 space long ; clypeus impunctate, smooth and shining ; abdo- 

 domen tapering more gradually and evenly to the apex than 

 with most Bombiis species. 



Males. — Head elongate, triangular, with long malar space : 

 antennae very long and slender ; posterior tibiag with outer sur- 

 faces distinctly concaved and bearing, for the most part, only 

 short hair ; traces of corbiculas not very distinct ; posterior 

 metatarsi bearing only short spines and pubescence, with no 

 long fringes, their outer faces distinctly concaved and finely 

 and evenly pubescent. 



Genitalia. — Outer spatha (fig. 138) from one-third to one- 

 half as long, along its middle line from anterior to posterior 

 border, as it is wide, from attachment to attachment ; its ante- 

 rior margin broadly, deeply and evenly incurved ; posterior 

 margin broadly and rather evenly outcurved, with a slight in- 

 dentation at the middle. Inner spatha with posterior part 

 strongly quadrangular, the apical half of this portion covered, 

 on lower surface, with a dense coat of hair, this hair usually 

 extending much farther forward along the sides than in the 



TRANS. AM. ENT. SOC, XXXVIII. (36) 



