THERMOREGULATION IN 4 SPECIES OF TROPICAL SOLITARY BEES - THE ROLES OF SIZE, SEX AND ALTITUDE

Body temperatures during free flight in the field, warm-up rates durin g pre-flight warm-up, and temperatures during tethered flight are meas ured for four tropical solitary bee species at three sites of differin g altitude in Papua New Guinea. All four species are capable of endoth ermic preflight warm-up; three species give slopes of thoracic tempera ture on ambient temperature of significantly less than 1, indicating r egulation of thoracic temperature. In the kleptoparasitic Coelioxys sp p. (Megachilidae) and Thyreus quadrimaculatus (Anthophoridae), warm-up rates and thoracic temperatures in flight are low by comparison with the two provisioning species Creightonella frontalis (Megachilidae) an d Amegilla sapiens (Anthophoridae). In both C. frontalis and A. sapien s thoracic temperatures correlate positively and significantly with bo th ambient temperature and body mass. In A. sapiens, body mass increas es with altitude; this can be interpreted as a response to lower ambie nt temperatures at higher altitude, an example of Bergmann's rule. In both A. sapiens and C. frontalis populations at higher altitude have h igher thoracic temperatures independent of differences of body mass, s uggestive of additional morphological or physiological adaptation to l ower ambient temperatures. In A. sapiens there is no qualitative diffe rence in body temperatures between males and females after controlling for body mass, while male C. frontalis have significantly lower thora cic temperatures than females of the species. This difference between A. sapiens and C.frontalis is discussed with reference to variation in mating systems found in the Apoidea.