Abstract
Acclimation in Anagasta kühniella pupae within the range of normal temperatures was not associated with changes in the rate of oxygen consumption or specific gravity of the haemolymph. Only when the pupae were conditioned at the extreme temperatures of 5 °C and 35 °C for about 16 and 8 hours, respectively, did their haemolymph become more concentrated. This was not due to desiccation. Thus the theory of osmoregulation does not explain the phenomenon of thermal acclimation satisfactorily.