Trophallactic activities in the honeybee brood nest - Heaters get supplied with high performance fuel

Honeybees actively regulate their brood temperature by heating between 33 and 36 degrees C if ambient temperature are lower. Heat is generated by vibrating the flight muscles. Heating rapidly depletes the worker's internal energy: therefore heating performance is limited by the honey that is ingested before the heating process. Stored honey is the predefined fuel for flying and heating but it is stored at a distance from the broodcomb, causing l potential logistic problem of efficient energy supply in the brood area. Our study focused on the behaviour and the thoracic temperature of the participants ill trophallactic food exchanges oil the broodcomb. We found that 85.5% of the recipients in a trophallactic food exchange have,I higher thoracic temperature during feeding contacts than donors and after the feeding contact the former engage ill brood heating more often. The donor bees have lower thoracic temperature and shuttle constantly between honey stores and the broodcomb where the transfer the stored honey to heating bees. Providing heat-emitting workers with small doses of high performance fuel contributes to an economic distribution of resources consistent with physiological conditions of the bees and the ecological requirements of the hive. The trophallaxis-based system is essential to provide the energy-intensive brood warming activity. The emerging independence from ambient temperature is not only beneficial for brood rearing during times of sudden cold spells, but also enables the honeybees in temperature regions to raise brood in early spring and might be the decisive factor for the occurrence of honeybees in temperate climates in general. (C) 2008 Elsevier GmbH. All rights reserved.