The study addresses the effects of higher and lower temperatures experienced during the
early stages of ontogeny on the parameters of the subsequent growth and development of the butterfly
Inachis io. The caterpillars reared at a temperature of 22°С during instars I–III and then transferred
to lower temperatures (16, 18, and 20°C) had higher instantaneous growth rates, larger body mass,
and shorter duration of instars IV and V than the caterpillars that developed permanently at these
lower temperatures. Vice versa, the caterpillars reared at 16°С during instars I–III and transferred
to higher temperatures (18, 20, and 22°C) developed and grew slower than the caterpillars reared at
these higher temperatures from the beginning. Possible physiological mechanisms underlying the
observed phenomena and their ecological consequences are discussed. Our results are compared
with the previously published data on fish—another group of ectothermic organisms, on which
similar experiments have been carried out.