The varied carpet beetle Anthrenus verbasci L. has a circannual pupation rhythm and pupates in the spring in the wild. The change in photoperiod acts as a predominant zeitgeber for this rhythm. However, it is unclear whether the change in ambient temperature acts as a zeitgeber. The present study examines the effects of lowâtemperature pulses on this circannual rhythm by exposing larvae kept under constant shortâday conditions (LD 12 : 12 h) at 20 °C to a lower temperature of 15, 10 or 5 °C for 8 or 12 weeks at various phases. Larval development and pupation are suppressed during exposure to low temperature, with this pupation being induced in sufficiently grown larvae within 2 months of a return to 20 °C. These results are attributed to the exogenous suppression and stimulation of pupation, rather than being related to the circannual rhythm (i.e. masking of the circannual rhythm by temperature). Furthermore, longâterm observations demonstrate the existence of phaseâdependent phase shifts of circannual rhythm as a result of lowâtemperature pulses. Circannual phase response curves to low temperature are constructed on the basis of the phase shifts obtained. A lowâtemperature pulse as a winter signal can reset the circannual rhythm of A. verbasci. It is probable that both temperature and photoperiod play a role in the entrainment of this circannual rhythm to a natural year.