NATURAL GROUPING OF BREMID.K. 407 



bumblebee species with which the present writer has come in 

 contact, while most of our Amarsipcea are comparatively gentle. 

 It will be interesting to see whether the various bumblebee 

 groups which have been established on the basis of structure are 

 really homogeneous species, when their habits are studied from 

 a taxonomic viewpoint. In the light of our present knowledge, 

 we should expect the seven American groups (cf. Franklin, *I2/ 

 '13) of the genus Bremus to belong to the biological subdivisions 

 as indicated in Table II. 



TABLE II. 



AMARSIPCEA. 



Phaneroschadonenta. 



1. Terrestris group. 



Cryptoschadonenta. 



2. Auricomus group. 10 



3. Fraternns group. 10 



4. Kirbyellus group. 11 



5. Pratorum group. 



MARSIPCEA. 



6. Borealis group. n 



7. Diimoucheli group. 



If Kriiger's ('16 and '20) subdivision of the Bremida into two 

 sections is really as far-reaching as it appears to be, we should 

 expect the members of the Borealis group to belong to the Mar- 

 sipcea, and those of the Kirbyellus group to the Amarsipcea, 

 since the spine is present in the former, but absent in the latter. 



It will also be interesting to investigate the methods which 

 the Bremidae employ in feeding the larvae ot the genus Psithyrus, 

 since certain species of the latter, e.g., Psithyrus variabilis, breed 

 in the nests of the Marsipcea, while others, e.g., Psithyrus ashtoni, 

 are parasitic on the Amarsipcea. 



Due to a lack of sufficient material, the writer has been unable 

 to determine whether the species for which Robertson ('03) 

 erected the genus Bombias have any clearly denned biological 

 peculiarities 12 which would serve as suitable biological characters 

 for distinguishing this group. 



10 Belonging to the genus Bombias of Robertson ('03). 



11 Probably. 



12 The males of this group, like those of closely related European species, have 

 their own peculiar habits (cf. Schmiedeknecht, '78; Hoffer, '82/'83; Robertson, 



