Abstract
The role of temperature as a time cue for the eclosion of adult Hyphantria cunea DRURY and its interaction with photoperiodic stimulus were experimentally analyzed. Experiments with various combinations of thermoperiods and photoperiods indicated that the timing of eclosion was determined not only by the light-off stimulus, but also was strongly affected by the stimulus of a drop in temperature. Further experiments showed that a change in temperature as well as in light, can act as a "phasing" factor in the endogenous circadian periodicity. However, the peak of eclosion occurred before the stimulus by a drop in temperature, while it occurred after the stimulus by light-off. This suggested the difference in the mode of action between these two stimuli. When animals were experimentally forced to make a choice between these two stimuli, it was revealed that a drop in temperature had stronger effect as the time cue for adult eclosion than light-off. Eclosion of the overwintered generation before dusk seemed to be caused by the drop in temperature at this season.
