1927] Nesting Habits of Some New England Bumble-Bees 123 
18 inches below the surface of the ground, and had entrance 
tunnels ranging from about 6 inches to 3 ft. in length. Most of 
the colonies did not average over 50 individuals; four, however 
were considerably larger; one, taken on July 12, 1923, consisting 
of the old queen, about 50 young queens, and over 150 workers, 
besides a large number of cocoons. Interspersed with the latter 
were about a dozen pollen cylinders, similar to those frequently 
found in the nests of Bremus affinis. These cylinders contained 
more than a quarter of a pound of pollen. 
In an earlier paper (1922a) attention was called to the fact 
that Psithyrus laboriosus is parasitic on Bremus vagans, while 
Psithyrus ashtoni is a parasite of Bremus affinis. In a letter, 
dated March 24, 1923, Professor 0. A. Stevens, of N orth Dakota 
Agricultural College, makes the following comment on the above 
statement: “I have supposed that Ps. laboriosus must be para- 
sitic on B. vagans here. Both species seem especially characteristic 
of the wooded area along the river. Ps. ashtoni is even more 
common, but B. affinis is rare, so some other host must be sought. 
I suspect B. terricola, but have no direct evidence as yet.” As in 
the case of Dr. Frison’s prediction in regard to the host of Psithy- 
rus laboriosus (cf. 1922a, p. 29), I am pleased to be able to confirm 
Professor Stevens’ surmise. On August 8, 1924, I took a nest of 
Bremus terricola which contained 3 workers, 3 young females of 
Psithyrus ashtoni , and several males and females of the latter 
species which had died in their cocoons before hatching. This is 
the only one of the fourteen nests of Bremus terricola in which 
young of Psithyrus ashtoni were reared, while 11 of the 36 Bremus 
affinis nests which have been examined were parasitized by this 
Psithyrus. 
In the summer of 1922, I took two nests of Bremus affinis , 
one of which contained (1) the old queen, 1 young queen, and 43 
workers of Bremus affinis; (2) 12 workers of Bremus affinis var. 
novce-anglice; and (3) 1 worker of Bremus terricola. The other 
contained (1) 23 workers of Bremus affinis; (2) 9 workers of 
Bremus affinis var. novce-anglice; and (3) 1 worker of Bremus ter- 
ricola. The heterogeneous nature of these two colonies led me 
to surmise that Bremus affinis var. novce-anglice might be a hy- 
brid between Bremus affinis and Bremus terricola , these two spe- 
