BEHAVIORAL THERMOREGULATION OF 6 NAMIB DESERT TENEBRIONID BEETLE SPECIES (COLEOPTERA)

We examined the postural adjustments and microhabitat shifts of 6 diur nal tenebrionid beetle species (Tenebrionidae: Adesmiinae) in the Nami b Desert under a wide range of environmental conditions. Microhabitat shifts were far more important than postural adjustments for controlli ng body temperature. Use of standard operative temperature models reve aled that 2 species, Physadesmia globosa (Haag) and Onymacris rugatipe nnis (Haag), maintain the lowest possible body temperatures in the hea t of the day by behavioral thermoregulation. Burying behavior frequent ly occurs at high body temperatures in most species in the heat of the day and may cause a significant reduction in body temperatures. Howev er, beetles may prefer to remain surface-active and avoid high tempera tures on the substrate by climbing bushes to feed there. Most postural adjustments resulted in no net or slight positive change in body temp erature 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 orde r to enhance cooling at high body temperatures.