THERMOREGULATION IN THE NEST OF THE NEOTROPICAL STINGLESS BEE SCAPTOTRIGONA-POSTICA AND A HYPOTHESIS ON THE EVOLUTION OF TEMPERATURE HOMEOSTASIS IN HIGHLY EUSOCIAL BEES

In the Brazilian stingless bee, Scaptotrigona postica, social thermore gulation was studied. Intranidal temperature was recorded in different parts of the nest and related to changes in ambient temperature. In a ddition, cooling and overheating experiments were carried out using co lonies in laboratory observation hives. The brood chamber is the warme st part of the nest, well insulated by a multi-layered involucrum. In the brood nest 32 +/- 3 degrees C were measured. In case of low aerial temperature the bees are capable of heating up the brood combs by mas s incubation. In addition, cold spots around the brood chamber are ins ulated by covering with cerumen, and the entrance is more or less clos ed. Overheating of the brood is reduced by accelerated and aligned fan ning and withdrawal of all the bees from the combs. Any direct cooling by evaporation of water could not be observed and probably is not nee ded in natural nests of Sc. postica which are built in trunk cavities of old trees in the neotropical rain forest. The importance of tempera ture homeostasis in the nest of stingless bees with perennial colonies and permanent brooding activity in tropical climate and a hypothesis on the evolution of thermoregulation in the highly eusocial Meliponida e and Apidae are discussed.