ILLINOIS STATE BEE-KEEPERS' ASSOCIATION 



69 



the equator of which was against the 

 glass. This shown as a circle of bees 

 on the glass exposing to view the cen- 

 ter of the cluster. 



It was then clearly demonstrated that 

 the cluster is not uniformly compact. 

 The cluster consists, between the combs 

 and sometimes above and below them, 

 of an outer shell of bees packed close 

 together with their heads toward the 

 center. The thickness of this ring 

 varies with the weather, being thicker 

 when the outer temperature is warm 

 and when less heat production is 

 needed and becoming thinner with the 

 increase in heat production. This is 

 because when more heat is produced 

 more bees are needed for this work, 

 leaving less for the outer rim. 



In order to expose this colony to 

 rapid changes in temperature, the hive 

 was placed on the roof of the building 

 and, while one person watched the bees, 

 another read the temperatures in the 

 room below, where the instruments 

 were located. A telephone was in- 

 stalled so that the two persons could be 

 in constant communication, head pieces 

 being used so that the hands of both 

 observers were free. The observations 

 made on the roof were then given over 

 the telephone and all records were 

 made below. This colony was of course 

 in the light, but the normal cluster was 

 nevertheless observed. The colony was 

 disturbed as little as possible during 

 the observations, to eliminate abnormal 

 conditions. 



The nearly spherical cluster of bees 

 consists, between the combs and some- 

 times above or below them, of an outer 

 shell of bees close together with their 

 heads toward the center. This ring 

 may be several layers tliick. The posi- 

 tion, 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 upward. The 

 bees in this outer shell are quiet except 

 for an occasional shifting of position. 

 Inside this rather definite shell the bees 

 between the combs are not so close 

 together nor are they headed in any 

 one way. Considerable movement, such 

 as walking, moving the abdomen from 

 side to side, and rapid fanning of the 

 wings, takes place inside the sphere 

 and when a bee becomes unusually ac- 

 tive the adjoining bees move away, 

 leaving an open space in which it can 

 m.ove freely. Two bees may often be 



seen tugging at each other. In addi- 

 tion to the bees between the combs, 

 placed as above described, others are 

 in 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 ex- 

 periment, 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 occupy- 

 ing 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 be- 

 tween the combs, are less active than 

 those in the interior of the cluster. 

 Naturally such a manipulation as this 

 is not to be recommended, except for 

 purposes of demonstration. 



It is clear from observations pre- 

 viously recorded that the highest tem- 

 peratures are those of points in the 

 center of this shell, and this is to be 

 expected, as the heat is generated here. 

 The outer shell constitutes an ideal in- 

 sulator for the conservation of the heat, 

 since the bees' arranged so close to- 

 gether form small dead air spaces in 

 their interlacing hairs, especially those 

 of the thorax, and afford still more in- 

 sulation with their bodies. The abdo- 

 mens of the bees in the outer row are 

 practically separate one from another, 

 and must often be exposed to seveTe 

 cold. That this method of conserving 

 heat is effective is shown by observa- 

 tions on undisturbed colonies out of 

 doors. For example, on January 14, 

 1914, there was at 9 a. m. a difference 

 of 68° F. between thermometers 14 

 (center of the sphere) and 16 (outside 

 the cluster) of Colony D, which were 

 less than 4 1-2 inches apart on the same 

 level in the same space between combs, 

 and a difference of 75° F. between this 

 couple and the bottom board 4 1-4 



