60 Beekeeping 



a warm-blooded animal, promptly cools if muscular activity 

 ceases and the surrounding air is cool. The temperature 

 changes of other colonial insects have not been studied, but 

 it would seem probable from our present knowledge that 

 the honeybee is the only insect which is able to generate 

 heat sufficient to maintain active movements without hiber- 

 nation throughout the winter in the North. 



The most interesting and important phases of the temper- 

 ature of the bee colony are to be observed in the winter 

 season and this will be discussed at the close of this chapter. 

 While many observations have been made on the temper- 

 ature of the bee colony during the period of brood-rearing, 

 the work has not been done with sufficient detail so that we 

 have little information concerning heat generation during 

 this season. The foregoing statement perhaps demands 

 some explanation. If a colony of bees is disturbed, 1 its 

 temperature promptly changes and consequently the inser- 

 tion of a mercurial thermometer into the brood nest, or even 

 an approach to the hive to read a thermometer already 

 inserted, may at times produce abnormal temperature 

 conditions. Furthermore, most of the thermometers used 

 are of doubtful accuracy and the slow action of a mercury 

 thermometer is an additional cause of inaccuracy. It is 

 usually stated that during brood-rearing a temperature of 

 approximately human blood heat is maintained within the 

 cluster and that this temperature is practically uniform. 

 The uniformity of the temperature has been greatly over- 

 estimated, at least in certain parts of the season, and it may 

 vary over several degrees. It rarely exceeds 97 F. How- 

 ever, if the temperature of the outside air exceeds the maxi- 

 mum hive temperature, the bees reduce the temperature of 

 the cluster by fanning, causing a drop in the temperature 

 inside the hive by evaporation. 



In the case of other insects, the length of the developmental 

 stages varies greatly, according to temperature. Since the 

 bee colony virtually creates its own temperature environ- 



1 This is specially true in winter when a definite cluster is formed. 



