Differential effects of temperature upon evening and morning peaks in the circadian activity of mosquitoes,Culex pipiens pallensandC. pipiens molestus

Abstract

In two subspecies of mosquito, Culex pipiens pallens and C.p. molestus, kept under LD 16: 8 the evening (E) and the morning (M) peaks of activity responded differently to changes of temperature. Molestus showed E and M which were phase‐advanced and ‐delayed, respectively, in response to lowering the temperature. In both mosquitoes, the inhibitory effect of low temperature is exerted upon M to a much larger extent than E. These facts suggest, on the one hand, that E and M are of different physiological nature and, on the other, that the circadian system involves some adaptive mechanism to the seasonal change of the daily temperature cycle. It seems too early to conclude, however, that E and M are underlain by separate circadian oscillations.