The Care of Bees in Winter 347 



undisturbed broodless bees generate virtually no heat 

 between 57° and 69° F. (Fig. 141). When the temperature 

 of the air about the bees falls below 57° the bees form a 

 cluster and raise the temperature, often almost to blood 

 heat. It follows that when the temperature of the bees 

 is above 57° and below 69° F. they do less work than at 

 other temperatures and their energies are thereby conserved. 

 However, to raise the outer temperature to 57° F. often so 

 reduces the relative humidity of the surrounding air as to 

 create excitement in the cluster and thereby to destroy the 

 desirable condition. Other factors not yet worked out 

 probably have a bearing on this problem. The majority 

 of beekeepers consider 40° to 45° F. as the best cellar tem- 

 perature, but it is clear that the temperature can usually 

 be raised to at least 50° F. with beneficial results. Humidity 

 and ventilation are so intimately connected with tempera- 

 ture that one cannot be investigated separate from the 

 others. 



Disturbance. 



Any factor which induces undue activity in the winter 

 must be considered as a disturbing factor. For example, 

 low temperature, improper humidity, poor food or insuffi- 

 cient ventilation create an undue excitement which should 

 be avoided. Disturbance is usually considered, however, as 

 applying to manipulation of the colony or to jarring while 

 the colony is clustered. Any such circumstance causes the 

 colony to raise the temperature, which may not again become 

 normal for many hours. All manipulation or handling is 

 to be avoided, therefore, especially in cold weather or in 

 the cellar. Colonies sometimes begin brood-rearing in 

 winter, usually induced by some improper outside condi- 

 tion. The care of the brood then causes a high temperature 

 and corresponding excessive activity which decimates the 

 colony. Brood-rearing should so far as possilple be avoided 

 until the bees can fly freely. 



In this connection it will be recalled that breeding often 



