68 O. E. PLATH. 



IV. SIZE OF COLONY AND NEST CAVITY. 



Wagner (1907, p. 36) states that the size of the nest cavity of 

 species which nest in the ground corresponds to the size of the 

 colony. In reply to this assertion, I may state that during the 

 summers of 1921 and 1922 I dug up a number of incipient bumble- 

 bee colonies whose nests filled less than half of the nest cavity. 



Although he has never actually observed this, it is further 

 claimed by Wagner (pp. 36, 153-154) that bumblebees excavate, 

 or at least enlarge, subterranean cavities for their nests. Sladen 

 (1912, p. 40), on the other hand, has the following to say con- 

 cerning this question: "As the larger and newer cocoons become 

 available for storage of food, the oldest ones at the bottom of the 

 comb are emptied and used no more, except in a time of plenty, 

 when all the rest are full. In underground nests, where all 

 available space is likely to be needed for the expansion of the 

 comb, the walls of these abandoned cocoons are often bitten 

 down, and the comb sinks. Wasps, it is well known, enlarge 

 their nest cavity according to their requirements by digging out 

 little lumps of earth and flying away with them, but I have never 

 seen bumblebees do this." To this statement, which agrees 

 with my own observations, I may add that the fragments of such 

 dismantled cocoons are sometimes found intermingled with the 

 material, e.g. dry grass, which with the bees cover the comb. 



V. THE PROXIMITY OF BUMBLEBEE COLONIES. 



Some years ago, Wagner (1907) discovered a colony of Bremus 

 muscorum, and about 35 cm. from it a destroyed bumblebee nest. 

 This led him to conclude that the members of the colony had left 

 the old nest and had built a new one, either because their larvae 

 had been destroyed by parasites or because they had been robbed 

 of their comb, for bumblebee colonies, according to Wagner 

 (P- I57)i never nest in such close proximity. In reply to this 

 assertion of Wagner (1907), I may state that I recently (June 26, 

 1922) discovered a colony of Bremus impatiens and one of Bremus 

 vagans which had their nests within two feet of each other, and, 

 judging from my experience with colonies in artificial nests, there 

 seems to be no reason why bumblebees could not nest in even 

 closer proximity. 1 



1 On July 29, 1923, shortly after the manuscript of this paper had been mailed 



