Comparative data were presented on the response of A. manducator to daily temperature rhythm (4 hours, 27 degree C, and 20 hours, 12 degree C) in darkness and under the conditions of a photoperiod with the ratio of 12:12 of darkness to light. Reactivation was observed only in the cases when high temperature was combined with the beginning or end of the scotophase. It was shown that changes in the activity of the neurosecretory system that determines activation are possible only under the conditions of simultaneous light-darkness and temperature signals, and under a definite status of thermophase in the daily cycle. The photoperiod not only establishes the status of thermophase in the daily cycle but also maintains the thermosensitive phase. none