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SUMMARYIn order to survive cold northern winters, honeybees crowd tightly together in a winter cluster. Present models of winter cluster thermoregulation consider the insulation by the tightly packed mantle bees as the decisive factor for survival at low temperatures, mostly ignoring the possibility of endothermic heat production. We provide here direct evidence of endothermic heat production by `shivering' thermogenesis. The abundance of endothermic bees is highest in the core and decreases towards the surface. This shows that core bees play an active role in thermal control of winter clusters. We conclude that regulation of both the insulation by the mantle bees and endothermic heat production by the inner bees is necessary to achieve thermal stability in a winter cluster.

-Drones and workers have completely different roles in a honeybee colony. This is reflected in many physiological, morphological and behavioural differences. Our overview mainly focuses on aspects of diet and metabolism in larvae and adults, and on the physiology of digestion. As larvae, drones have different protein and sugar requirements than workers, and in each life stage drones and workers differ in body composition (percentages of glycogen, lipids and proteins). Like queens, drones as adults are nourished by worker-prepared food, and compared to workers their ability to digest is reduced. Mature drones fly usually only under optimal weather conditions. Their flight metabolism and resting metabolism also differ from those of workers. We discuss these differences as adaptations to the different functions of the two sexes within the colony as a superorganism.nutrition / digestion / enzymes / energy metabolism / body reserves

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-Pollen foragers quickly sense increases in colony pollen stores, and modify their foraging activity appropriately. In association with these changes in foraging behavior, nurse bees transfer a larger portion of newly synthesized 14 C-phenylalanine-labeled protein to the foragers.These findings support the hypothesis that trophallactic interactions between nurse bees and pollen foragers may serve as a cue apprising pollen foragers of the colony's need for pollen.© Inra/DIB/AGIB/Elsevier, Paris pollen forager / protein trophallaxis / nurse bee