14 BULLETIN 93, U. S. DEPARTMENT OF AGRICULTURE. 



the bees did not have roomj for a spherical cluster, they formed a 

 ring on the glass. Thermometers were then placed close together in 

 the outside space, so that the temperatures of various points could 

 be determined as desired. This hive was on the roof, and, while one 

 person watched the bees, constant communication could be kept up 

 with the person reading the temperatures in the room below by means 

 of a telephone, arranged so that the hands of both observers were 

 free. This colony was of course in the light, but the normal cluster 

 was nevertheless observed. It was disturbed as little as possible. 



The nearly spherical cluster of bees consists, between the combs 

 and sometimes above or below them, of an outer shell of bees close 

 together with their heads toward the center. This ring may be several 

 layers thick. The position with the heads inward is typical, except 

 when condensed moisture drops on the cluster as it often does in cool 

 weather, when the bees at the top turn so that their heads are up- 

 ward. The bees in this outer shell are quiet except for an occasional 

 shifting of position. Inside this rather definite shell the bees be- 

 tween the combs are not so close together nor are they headed in any 

 one way. Considerable movement, such as walking, moving the abdo- 

 men from side to side, and rapid fanning of the wings, takes place 

 inside the sphere and when a bee becomes unusually active the ad- 

 joining bees move away, leaving an open space in which it can move 

 freely. Two bees may often be seen tugging at each other. In 

 addition to the bees between the combs, placed as above described, 

 others are in the empty cells of the comb on which the cluster is 

 always formed, always with their heads in. A verification of these 

 statements is contained in the following observations, and the ex- 

 periment may easily be repeated by anyone. For the purpose of 

 obtaining a colony without combs for another experiment, a hive was 

 opened December 15, 1913, while the outside temperature was low 

 enough to cause the formation of a compact cluster. When the combs 

 were separated the circle of bees in the shell was clearly observed. 

 When a comb from the center of the cluster was shaken the active 

 bees in the center of the circle dropped off readily, and those in the 

 outer shell which were somewhat sluggish were removed with more 

 difficulty. After this was done those occupying empty cells in the 

 center of the sphere backed out of the cells and were shaken off. 

 Finally those occupying cells in the border of the sphere backed out, 

 showing a well-marked circle on the combs. Evidently the bees in 

 the shell, whether in the cells or between the combs, are less active 

 than those in the interior of the cluster. Naturally such a manipu- 

 lation as this is not to be recommended, except for purposes of 

 demonstration. 



It is clear from observations previously recorded that the highest 

 temperatures are those of points in the center of this shell, and this is 



