Do you have reference supporting that outer bees
push to the center of the cluster?  I would love to 
see any related info. Thanks 


> The behavior of individual workers in clusters has been investigated by Esch (1960). He observed that workers in the outer shell hang together with neighboring workers almost motionlessly with almost no difference in their thoracic and abdominal temperatures. However, shell individuals occasionally move into the center of the cluster, when their thoracic temperatures jump almost 10°C, from 23-27° to 33-37°C, within minutes. They may remain in the cluster center for up to 12 hr, increasing thoracic temperature whenever it begins to fall, and eventually rejoining the shell workers. Thus, the cluster can be thought of as a dynamic system in which heat is generated metabolically in the loose center cluster and retained by the tighter insulating outer shell, with individuals performing both warming and insulative tasks at different times. 

SOURCE:
Winston, M. L. (1991). The biology of the honey bee. Harvard University Press.

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