84 THE CANADIAN ENTOMOLOGIST 



INQUILINE BUMBLE-BEES IN BRITISH COLUMBIA. 



BY F. W. L. SLADEN, APICULTURIST, CENTRAL EXPERIMENTAL FARM, 



OTTAWA. 



Having been informed by Mr. R. C. Treherne of a nest of 

 bumble-bees in his garden at the foot of the mountain at Agassiz, 

 B. C, I dug it up on July 7, 1914. The nest was found at about 

 18 inches from the surface. It contained an old queen of Bonihus 

 flavifrons and about half a dozen workers of the same species; 

 also the well-preserved body of a female of Psithyrus insularis Sm., 

 and several unopened cocoons, out of one of which I extracted a 

 male, nearly ready to hatch, of Psithyrus consultiis Frank. The 

 occurrence of Psithyrus in this nest is of considerable interest, 

 for Franklin said in his recent monograph of the Bombidae of 

 North America (Trans. Am. Ent. Soc. XXXV, page 448), "There 

 is not yet a single new world account of a Psithyrus having been 

 found in a bumble-bee's nest." 



Moreover, several noteworthy conclusions are indicated. 



Corroboration of a new and highly convincing kind is given 

 to the already well-founded belief (id., page 458), that consultus 

 is the male of insularis, for the female insularis was in all probability 

 the mother of the male consultus. It may be remarked that the 

 name insularis has priority. 



Second, Ps. insularis is evidently parasitic upon B. flavifrons 

 in British Columbia. In Eastern Canada {insularis is common at 

 Ottawa) it must prey upon some other species of Bombus, for 

 flavifrons is not found in the east. Probably, however, it lives 

 with several species in both regions. 



Third, Ps. insularis does not apparently kill the Bombus queen, 

 as I have found Ps. vestalis and rupestris do in England ("The 

 Humble Bee," page 60), but both females seem to live together in 

 the nest, laying eggs. (The death of the insuralis female was 

 evidently due to age or accident.) This seems to be in accord 

 with Hoffer's observations on Psithyrus campestris, the Old World 

 representative of insularis. He found Ps. campestris living on 

 good terms with its hosts, B. agrorum and helferanus, both queens 

 producing young (Die Schmarotzerhummeln Steirmarks, page 101). 



March, 1915 



