1916] The Sleep of Insects 243 



An examination of the surrounding vegetation revealed no 

 others, although the swarm was buzzing impatiently about 

 awaiting a quiet chance to alight. So we left the spot and 

 returned an hour later. Now we found the 28 bees clustered 

 near the tops of a small clump of stalks. Since it was now 

 almost dark, my presence did not disturb them. They were 

 huddled together in groups of 2 to 5, with only 3 insects occupy- 

 ing their sites singly. They were settled for the night in their 

 characteristic posture, resting on their support with the head 

 downward, the abdomen ventrally curved as far as their chubby 

 forms would permit. 



It is hard to refrain from calling this a case of protective 

 environment rationally chosen by the insect. I surely would 

 not have seen their brown bodies blending with the dingy 

 burned leaves, had I not known just where to look for them. In 

 another field about a quarter of a mile distant the sweet clover 

 was abundant, but a careful search revealed no bees. 



The next evening 29 bees, only one more, were asleep on 

 these five stems, all clustered on the apical three inches of the 

 dead plants. On the top of another plant ten feet away, 2 

 were at rest. All were in the same characteristic position. If 

 they had chosen this site for protection alone they would have 

 rested singly on the plants, but since they huddled in groups, 

 they must have sought sociabihty also. They were so close 

 together in some cases as to arouse my suspicion about their 

 mating, but a close examination proved the idea false. 



The fohowing night, July 21, 24 of these bees were here to 

 spend the night in the same way. On the 22nd, 30 were present. 

 On this evening I marked part of them with white paint in 

 order to make sure whether this uniform group was made up 

 of the same individuals night after night. As fate would have 

 it, by the next evening a cow had broken down their chosen 

 stems, so none of the bees were there. However, 15 were found 

 on similar weeds near by; 7 of these bore the white markings. 

 This gave evidence sufficient to prove that the same bees return 

 to their chosen spot regularly. Part of these were taken to see 

 whether one or both sexes were thus gregarious; of the 18 taken, 

 all were males. They made no attempt to move when picked 

 up with the forceps, while earlier in the evening they could not 

 be approached without a heavy buzzing and flying about. 



