Temperature tolerance and water balance in feral and domestic honey bees, Apis mellifera L.

Feral and domestic honey bees were compared to determine relative levels of adaptation to the Arizona desert. Feral honey bees were more tolerant to high temperatures than domestic honey bees. Monthly critical thermal maxima (CTMs) of feral bees were significantly different from those of domestic bees (P < 0.001). The highest mean CTM for feral bees was 50.7 ± 1.0°C, and for domestic honey bees was 42.8 ± 2.8°C; both were recorded in June 1991. There was also a significant effect of sampling date on CTMs (P < 0.0001). Water loss increased with increasing temperature and with decreasing humidity for both feral and domestic honey bees. The rates of water loss for both types of bees were highest in dry air (0% relative humility) at 35°C, with the average value of 6.82 ± 0.33 mg/g/hr for domestic bees. At 35°C, the rate of water loss of feral bees was more than twice that at 25°C (5.94 compared with 2.37 mg/g/hr). Water losses for feral and domestic honey bees were not significantly different; therefore, rates of water loss do not explain the higher temperature tolerance of feral honey bees.