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 accomplishes by placing colonies 
