Behavioral Thermoregulation of Six Namib Desert Tenebrionid Beetle Species (Coleoptera)

Abstract

We examined the postural adjustments and microhabitat shifts of 6 diurnal tenebrionid beetle species (Tenebrionidae: Adesmiinae) in the Namib Desert under a wide range of environmental conditions. Microhabitat shifts were far more important than postural adjustments for controlling body temperature. Use of standard operative temperature models revealed that 2 species, Physadesmia globosa (Haag) and Onymacris rugatipennis (Haag), maintain the lowest possible body temperatures in the heat of the day by behavioral thermoregulation. Burying behavior frequently occurs at high body temperatures in most species in the heat of the day and may cause a significant reduction in body temperature. However, beetles may prefer to remain surface-active and avoid high temperatures on the substrate by climbing bushes to feed there. Most postural adjustments resulted in no net or a slight positive change in body temperature at high body temperatures. There was no common posture adopted by all species in the same temperature range. Contrary to theory and empirical data for other insect species, we found little evidence that these beetles stilted (elevated the body above the substrate) in order to enhance cooling at high body temperatures.