Temperature Regulation and Energetics of the Solitary Bee Centris pallida during Foraging and Intermale Mate Competition

Publisher Website
Google Scholar
Abstract
Solitary bees (Centris pallida Fox; Hymenoptera: Anthophoridae) were observed during diurnal activity in a hot desert environment. Females foraged throughout the day in flowering paloverde trees; males divided their time between foraging and hovering in search of receptive females. Thoracic temperatures ( ) of both sexes were high. Foraging males and females had averaging 44-46 and 43-45 C, respectively. The of hovering males averaged about 44 C in the early morning and 47 C from midmorning until activity ceased. Thoracic temperatures of both sexes changed by 3-4 C over an ambient temperature ( ) range of 25-40 C. Abdominal temperature ( ) was consistently about 4.5 C above , and there was no indication of augmented heat transfer between thorax and abdomen at high . Maximum tolerable was 50-51 C. Evidence for evaporative heat loss was equivocal for artificially heated bees, but free-flying animals showed little indication of use of evaporative cooling. Energy metabolism (measured as oxygen consumption) during flight (1. 1 W/g thorax) resembled that of other endothermic insects of similar mass; mass-specific thermal conductance (0.034 W/[g thorax - C]) was slightly larger than predicted from body mass. Centris pallida probably controls body temperature by reducing flight at high . Nevertheless, hovering males often attain within 2-3 C of lethality.