1922] Notes on Nesting Habits of North American Bumblebees 195 



Franklin (1912/13, I, p. 309) says that the workers of this 

 species are "very waspish," a statement which is corroborated 

 by my experiences. 



II, Br emus impatiens Cresson. 



Putnam (1865, p. 101) reports taking a nest of this species 

 under an old stump, in an orchard, but gives no further details, 

 while Frankhn (1912/13, I, p. 313) has the following to say con-, 

 cerning the nesting habits of this bumblebee: "I have taken 

 several nests of this species and have known of their being taken 

 by others and, as far as I have been able to ascertain, they are 

 invariably subterranean and the colonies often consist of a very 

 large number of individuals." On August 31, 1904, the same 

 author took a nest of Bremus impatiens, at Amherst, Mass. 

 It was about 2i ft. below the surface of the ground and con- 

 tained 4 queens, 15 males, 321 workers, and 330 unbroken cells, 

 154 of which were queen cells. 



I took 16 nests of this species during the summers of 1921 and 

 1922. Of these 16 nests, 11 were discovered in, and 5 near, the 

 Arnold Arboretum, one of the latter being taken on the grounds 

 of the Bussey Institution. All of these 16 nests, as well as several 

 others which were not dug up, were subterranean. They were 

 from 1 to 3 ft. below the surface, and had tunnels varying from 

 18 inches to 5 ft. in length. A number of these nests were situated 

 in decayed stumps. Most of the colonies were verj^ populous, 

 the largest one consisting of over 450 workers (August 4, 1921). 

 Five of the nests taken during the early part of the summer 

 contained, in addition to the queen which "ruled" the nest, 

 from 1 to 4 dead impatiens queens. 



One of the 16 colonies was parasitized by a Psithyrus be- 

 longing to the Laboriosus Group. This nest, on August 8, 1922, 

 contained (1) 17 males and about 75 workers of Bremus impatiens, 

 as well as the well-preserved body of the old queen; and (2) 

 the old queen and 2 males of Psithyrus. During the next few 

 weeks, a considerable number of Bremus and Psithyrus males, 

 and several Psithyrus females, were reared from this Brcmus- 

 Psithyrus colony. 



