From 1,200,000 thermocouple temperature determinations made in beehives during the winter, the following information was obtained:

Temperature readings permit determination of the cluster size, shape, movement, and brood-rearing activities.

The 44°F. isotherm establishes the  outermost limit of the winter cluster.  

The unprotected (check) colonies had the tightest insulating shell, or the least distance between the 44° and 60° isotherms.

A colony protected by insulation will have a less compact cluster that will fluctuate more in size with temperature change than a cluster in an unprotected colony. 

Insulated colonies start brood rearing a few days earlier than unprotected colonies, but  the latter tend to catch up shortly after warmer  weather arrives.

As high as 100° was recorded in some seemingly normal clusters when the outside temperature was relatively uniform and moderate. 

The temperature within the cluster varies, but under normal conditions it is not closely correlated with outside temperatures. 

Honey bees make no attempt to maintain the temperature in the domicile outside the  winter cluster.

Under normal winter conditions either  insulated or noninsulated colonies should survive at Madison, Wis. 

THE THERMOLOGY OF WINTERING HONEY BEE COLONIES. Technical Bulletin No. 1429

Issued November 1971. U.S. Government Printing Office Washington, D.C. 20402

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