BULLETIN OF THE 



No. 93 



Contribution from the Bureau of Entomology, L. O. Howard, Chief, 

 April 30, 1914. 



THE TEMPERATURE OF THE HONEYBEE CLUSTER 



IN WINTER. 



By E. F. Phillips, Ph. D., In Charge of Bee Culture Investigations, and 

 George S. Demtjth, Apicultural Assistant. 



INTRODUCTION. 



The care of bees in winter is one of the most perplexing problems 

 confronting the beekeeper, especially in the North. This appears to 

 be due chiefly to the fact that it is difficult to determine by direct ob- 

 servation the normal activities of the bee colony in winter, and conse- 

 quently it is well-nigh impossible to determine what external condi- 

 tions are most favorable except by the gross results of experience. 

 Nor can we by a study of our wintering successes and failures deter- 

 mine definitely whether the same conditions of temperature and 

 humidity are desirable throughout the entire winter. On account, 

 therefore, of the lack of accurate knowledge of the activities of bees 

 in the winter season this problem has been taken up with the aid of 

 certain special apparatus and equipment. This preliminary report is 

 not to be considered as giving definite recommendations as to the care 

 of bees in winter, but rather is issued to make known to beekeepers 

 some of the interesting results obtained in the first season's work on 

 the behavior of the bees during the winter season. 



American beekeepers lose thousands of dollars annually in winter 

 from the actual death of colonies and even still more from those 

 colonies that do not die, but which are reduced in numbers and 

 vitality. The wintering problem is therefore a vitally important one. 

 The factors influencing the welfare of the colony and the behavior 

 of the bees are numerous and closely interrelated. Of the chief ones 

 may be mentioned external temperature, food, ventilation, humidity, 

 the condition of the colony at the beginning of winter, and various 

 forms of irritation. In the present paper special emphasis is placed 

 on heat production, by which is meant the responses of the bees of 

 the cluster to the outer temperature and to changes in the outer tem- 

 perature as manifested in the generation of heat by the bees. 



Note. — This bulletin presents studies of bees as affected by temperature conditions 

 during winter and is of special interest to beekeepers in the North. 

 36157°— Bull. 93—14 



