BENNETT, V.A.*; LEE, R.E.; KUKAL, O.: Abiotic and biotic factors affecting water loss rates in the polar desert caterpillar Gynaephora groenlandica (Lepidoptera: Lymantriidae) and the temperate caterpillar, Pyrrharctia isabella (Lepidoptera: Arctiidae)

Water conservation is critical for inhabitants of polar deserts, such as the arctic woollybear caterpillar (Gynaephora groenlandica). Although G. groenlandica showed a significant decrease in rate of CO₂ release, water loss rates did not decrease significantly upon entry into hibernation. However, the temperate woollybear caterpillar, Pyrrharctia isabella showed a significant seasonal reduction in rates of both water loss and CO₂ release upon entry into hibernation. In addition, the CO₂ emission efficiency (the ratio of water lost to CO₂ released), which reflects the amount of water lost via respiration, was significantly lower in G. groenlandica than in P. isabella under all conditions. This evidence suggests that G. groenlandica is well-suited to tolerate the desiccating conditions of the polar desert year-round. Water loss rates were significantly higher in flowing air than in still air. Setae significantly reduced the desiccating effects of flowing air on cuticular water loss in G. groenlandica by providing a boundary layer around the animal surface, thus reducing localized vapor pressure gradient. The lowest water loss rates were observed under simulated hibernaculum conditions of still air, low temperature, and high relative humidity for G. groenlandica.