The varied carpet beetle Anthrenus verbasci shows a clear circannual pupation rhythm
under light/dark (LD) 12:12. We examined whether this rhythm is exhibited under
constant light (LL) of 0.002 Wm-2 and 0.9 Wm-2 intensities. Rhythmic pupation was not
observed when the larvae were continuously maintained under LL. Moreover, the
circannual rhythmicity of pupation was not observed under LL after preexposure to LD
12:12 for 2 or 4 weeks but was observed after exposure for 8 weeks. Under LL of both
light intensities, as the preexposure to LD 12:12 was longer, the first pupation peaks
occurred earlier and almost synchronized by preexposure for 8 weeks with the first peak
under continuous LD 12:12. However, the transition from LD 12:12 to LL did not reset
the phase of this circannual rhythm. Preexposure to LD 12:12 probably synchronizes the
asynchronous rhythm observed under LL so that a clear circannual pupation rhythm is
exhibited.