396 O. E. PLATH. 



the nine subgenera established by Vogt ('n), has divided the 

 genus Bremus into two sections, on the basis of the presence or 

 absence of a spinous projection on the posterior, distal angle of 

 the metatarsus of the middle legs. This character may prove of 

 considerable importance in determining the genetic relationship 

 of the various species of bumblebees, since, as we shall see later, 

 it seems to go hand in hand with certain fundamental differences 

 in the method by which these insects feed their larvae. 



Another independent subdivision of the non-parasitic bumble- 

 bees on the basis of structure is that by Robertson ('03), who re- 

 moved certain species from the genus Bremus (Bombus) and 

 erected the genus Bombias, chiefly on the basis of the size and 

 position of the ocelli. This innovation does not seem to have 

 found favor with European workers, but Bombias, either as genus 

 or subgenus, is in common use in the United States. 



Among the attempts to divide the Bremidae into natural groups 

 on the basis of structure, we may also include that of Friese and 

 von Wagner ('10), who constructed a "Stammbaum" which is 

 intended to show the probable genetic relationship of the fifteen 

 species of Bremus occurring in Germany. This scheme of group- 

 ing will, no doubt, have to be considerably modified, since it is 

 not in harmony with certain fundamental biological and struc- 

 tural characters which have been pointed out by Sladen ('99 and 

 12) and Kriiger ('16 and '20). 



GROUPING ON THE BASIS OF HABITS. 



The first one who used biological characters for subdividing 

 the Bremidae was the English entomologist Smith ('76). In the 

 second edition of his "Catalogue of British Bees," he divides 

 the English species of the genus Bremus into Surface-builders 

 (Section I.) and Underground-builders (Section II.). While this 

 method of subdividing the Bremidae may be of some value to the 

 amateur naturalist, it is of little importance for taxonomic pur- 

 poses, since certain species of bumblebees, e.g., Bremus vagans, 

 make use ot many diverse nesting sites: underground, on the 

 surface, in stone walls, hollow trees, birds' nests, attics, fur 

 coats, etc. 



A more promising and dependable biological character for 



