I understand that mantle bees are engaged in survival against the onset of a chill coma. Since heat flows to cold (Zeroth Law of Thermodynamics – Thermal Equilibrium), it's hard to imagine how they would be a part of heating the cluster. It seems that whatever heat they generate would flow in the opposite direction toward the cooler envelope and hive components. There is plenty of IR photography showing comb images from the core to the outer mantel. The bees on the outer mantle show temps in the high 40s and low 50s f. Compared to heater bees in the 108 f range. 

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html