The Cycle of the Year 91 



side the cluster may sometimes be 100° F. warmer than a 

 point a few inches away but outside the cluster. The 

 number of inactive bees varies with the outer temperature, 

 being larger at warmer temperatures when less heat produc- 

 tion is required and smaller when more bees are engaged in 

 activities involved in heat production. 



Source of heat. 



Within the hollow sphere are bees which move about 

 freely, these being the ones most concerned in heat genera- 

 tion. They produce heat by muscular activity, such as 

 movements of the legs and abdomen, but perhaps most 

 effectually by vigorous fanning. The bees which form the 

 shell constantly shift their positions and exchange places 

 with bees from within. A bee from the center forces its 

 way head first through the shell, then turns around and 

 remains for a time on the outside layer. The shifting seems 

 to be more rapid in cold weather than in mild. 



Effect of accumulation of feces. 



During the winter, the bees consume the honey stored dur- 

 ing the summer. The undigested portion, which forms 

 excreta, is retained in the rectal ampulla (hind-intestine) 

 until the bees have opportunity for flight, for normally no 

 feces are deposited by the workers within the hive. Dur- 

 ing the cold winters of the North there are times when 

 bees cannot fly for several weeks and the generation of heat 

 during such a period of cold weather requires increased 

 consumption of food and causes an increase in the amount 

 of feces. The presence of feces, on the other hand, causes 

 the bees to become restless, to generate still more heat (see 

 Fig. 145) and to accumulate still more feces. Apparently 

 a colony in winter confinement is in the confines of a vicious 

 circle and the successful wintering depends preeminently 

 on good food. If, however, the colony is so placed that 

 little or no heat must be produced, the situation is relieved 

 and this the beekeeper accompUshes by placing colonies 



