UNITED STATES DEPARTMENT OF AGRICULTURE 



wmA BULLETIN No. 988 



Contribution from the States Relations Service 

 A. C. TRUE, Director. 





Washington, D. C. 



PROFESSIONAL PAPER 



December 5, 1921 



HEAT PRODUCTION OF HONEYBEES IN WINTER. 



By R. D. Milnee, formerly Assistant Chief of the Office of Home Economics, 

 States Relations Service, and Geo. . S. Demuth, formerly Apicultural Assist- 

 ant, Bureau of Entomology. 



Source of heat in winter cluster 



Outline of the experiment 



Discussion of the temperature re- 

 sponses in this experiment 



CONTENTS. 



Page. 

 3 

 4 



Method of measuring the work done 



by the cluster 6 



Results obtained in the experiment- 8 



Summary 14 



Studies of the behavior of honeybees in winter x show that these 

 insects do not hibernate, but throughout the entire winter they con- 

 sume their stores of honey and generate heat. The results of these 

 studies further show that after the winter cluster is formed, at 14° C, 

 there is an inverse relationship between the temperature inside and 

 outside the cluster, and that the generation of heat to warm the 

 winter cluster is solely by muscular activity, such as fanning of the 

 wings and other movements. These results do not agree with the 

 conclusions of Parhon 2 that the honeybee is in part heterothermic. 

 The work on behavior of the bees during winter, from which the 

 practical conclusions as to the needs of bees in winter were drawn, 

 was chiefly on temperature responses, and no data were available 

 as to the actual heat production of the bees during this season. The 

 work herein recorded was begun in order that the missing data might 

 be in part obtained. 



From many observations it has long been known that the duration 

 of life of the individual worker bees is determined by the work which 



1 U. S. Dept. Agr. Bui. 93 (1914), The Temperature of the Honeybee Cluster in Winter. 

 By Phillips and Demuth. See also Farmers' Buls. 695, 1012, and 1014. 



2 Parhon, Marie, 1909. Les echanges nutritifs chez les abeilles pendant les quatre 

 saisons. Paris : Masson et Cie. 57 pp. 



55663°— 21 1 



