A test of the ‘maxithermy’ hypothesis with three species of tenebrionid beetles

Abstract

Hamilton invoked his ‘maxithermy’ hypothesis, which suggests that the high body temperatures of desert tenebrionid beetles are sustained because they lead to increased rates of many biological processes, and are therefore advantageous. I designed an experiment to test the validity of the ‘maxithermy’ hypothesis in three species of Namib desert beetles (Onymacris plana, O. rugatipennis and Physadesmia globosa) known to have high body temperatures. Moreover, this experiment examined the ability of these ectothermic beetles to reduce their metabolic rates in times of food shortage, by choosing lower environmental temperatures. None of the three species changed the selected environmental temperature with progressive food deprivation. This experiment rejects the ‘maxithermy’ hypothesis as an adaptive hypothesis to explain high body temperatures.