The role of nest surface temperatures and the brain in influencing ant metabolic rates

Thermal limits of insects can be influenced by recent thermal history: here we used thermolimit respirometry to determine metabolic rate responses and thermal limits of the dominant meat ant, 'Iridomyrmex purpureus'. Firstly, we tested the hypothesis that nest surface temperatures have a pervasive influence on thermal limits. Metabolic rates and activity of freshly field collected individuals were measured continuously while ramping temperatures from 44°C to 62°C at 0.25°C/minute. At all the stages of thermolimit respirometry, metabolic rates were independent of nest surface temperatures, and CTmax did not differ between ants collected from nest with different surface temperatures. Secondly, we tested the effect of brain control on upper thermal limits of meat ants via ant decapitation experiments ('headedness'). Decapitated ants exhibited similar upper critical temperature (CTmax) results to living ants...