Effect of variability of breeding temperature on the thermal responses of a poikilothermic insect, the female cockroach Blaberus craniifer

1. 1.|The body temperature, T b, of female cockroaches Blaberus craniifer exposed to controlled variations in ambient temperature, T a, was precisely monitored. The curves were fitted to a first-order Newtonian model and compared to those obtained in similar conditions with an inert replica. Although the fit was fairly good, insect curves significantly differed from those of the passive system. 2. 2.|Compared with animals raised at a variable temperature (27 ± 2.5°C), the variability of the parameters of the model was much increased in animals raised at a stable temperature (27 ± 0.5°C). This corroborates our previous findings on the existence of increased morphological and behavioural variability in the latter conditions. 3. 3.|In view of these differences, it is proposed to restrict the term poikilothermy to ectothermic animals who have actually lived in a thermally variable environment, and to designate by apoikilothermy the status of ectothermic animals who have only experienced a very constant ambient temperature.