OBSERVATIONS ON BUMBLEBEES. 75 



optera, they are, as the following observation shows, nevertheless 

 very industrious and efficient creatures. On August 5, 1921, I 

 placed about 50 workers belonging to a large colony of Bremus 

 impatiens in a glass-covered box and provided them with honey 

 (in a porcelain dish) and five pieces of old bumblebee comb, each 

 consisting of about a dozen empty cocoons. The bees started 

 at once to repair three of the pieces of comb with wax which 

 they took from the other two. In the course of a few hours, 

 nothing remained of these two pieces of comb except a few 

 shreds, and the remaining three were completely renovated and 

 filled with honey. The rapidity with which this work was 

 carried out shows that Wagner's (1907) claim is an exaggeration. 



XIX. ON THE HIBERNATION INSTINCT OF BUMBLEBEES. 



Wagner (1907) claims that the psychic qualities of social 

 insects are no higher, and in some cases even lower, than those 

 of solitary insects. As proof for this contention he cites (p. 196) 

 the "fact' ! that the queens of bumblebees and social wasps 

 overwinter singly, while certain solitary bees, e.g. Xylocopa, 

 hibernate in groups. That these assertions of Wagner (pp. 195- 

 196) are incorrect, at least as far as social wasps are concerned, 

 is shown by recent observations of Mr. and Mrs. Rau (1918), 

 who found that the queens of some of our North American 

 wasps congregate for hibernation; and, as the following observa- 

 tions indicate, there also seems to be a tendency in this direction 

 in bumblebees. In artificial overwintering experiments, Lind- 

 hard (1912) found as many as eleven Bremus queens hibernating 

 close together, and I was able to make similar observations out 

 in the open. On October 15, 1922, I dug up within an area 

 of less than two square feet 21 queens of Bremus impatiens, 

 many of which were hibernating in groups of two and three. 

 In dealing with this question, Wagner (p. 196) furthermore 

 overlooked the fact that bumblebee colonies in certain parts of 

 the tropics are probably perennial (cf. von Ihering, 1903). 



Equally incorrect is Wagner's (p. 9) surmise that a spot free 

 from grass constitutes one of the conditions for the young 

 bumblebee queen in the choice of her hibernaculum, for the 

 spot in which the 21 queens were hibernating was completely 

 covered with grass. 



