UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 988 
Contribution from the States Relations Service 
A. C. TRUE, Director. 
S)JS"&-ru 
j&fi&j-u 
Washington, D. C. 
PROFESSIONAL PAPER 
December 5, 1921 
HEAT PRODUCTION OF HONEYBEES IN WINTER. 
By R. D. Milner, formerly Assistant Chief of the Office of Home Economics, 
States Relations Service, and Geo. S. Demuth, formerly Apicultural Assist- 
ant, Bureau of Entomology. 
CONTENTS. 
Source of heat in winter cluster 
Outline of the experiment 
Discussion of the temperature re- 
sponses in this experiment 
Page. 
3 
4 
Page. 
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 1 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. BuL 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 
