124 
Psyche 
[April 
cies being closely related. Since then, however, four more mixed 
colonies of these two species have been taken, two of which 
contained a much greater proportion of terricola workers than 
the two nests found in 1922. The first of these four mixed 
colonies was taken July 3, 1923. It consisted of the old queen 
and 6 workers of Bremus affinis, and 1 worker of Bremus ter- 
ricola. The second was taken on August 9, of the same year, 
and contained the old queen and about 75 workers of Bremus 
affinis, and 1 worker of Bremus terricola. The remaining two 
were both discovered in 1926, one being taken July 5, and the 
other July 8. The first of these consisted of (1) the old queen 
and 29 workers of Bremus affinis, (2) 7 workers of Bremus ter- 
ricola, and (3) a female of Psithyrue ashtoni and a considerable 
quantity of Psithyrus brood in various stages of development. The 
other consisted of 15 workers of Bremus affinis, 3 of Bremus ter- 
ricola, and some brood of Psithyrus ashtoni which hatched later. 
No additional workers of Bremus terricola hatched from any of 
these six nests, the first four producing only young of Bremus 
affinis and, the last two nothing but Psithyrus ashtoni. 
As was suggested recently in a joint paper with Dr. Bequaert 
(1925), the difference in coloration between the typical form of 
Bremus affinis and its variety novce-anglice is probably due to 
environment rather than hybridism. The presence of the work- 
ers of Bremus terricola in 6 of the 36 affinis nests is easily explain- 
ed by “natural requeening,” a subject which I discussed in a 
recent paper (1924), the only difference being that in this case, 
as with Bremus lucorum and Bremus terrestris in Europe (cf. 
Sladen 1912), requeening is accomplished by a closely related 
species. 
To these data may be added some observations of Professor 
0. A. Stevens, who informs me that he found a populous nest of 
Bremus terricola under the floor of a shed, the bees entering by a 
hole in the roof. 
Pratorum Group. 
1. Bremus per plexus Cresson. 
What is known about the nesting habits of Bremus perplexus 
we owe to Franklin (1912-13) who took two nests in Vermont, 
early in August. Both were situated in the walls of houses, and 
