Circadian clock in insect photoperiodism.

Night-interrluption experiments with the wasp Nasonia vitripennis maintained in 48- and 72-hour light: dark cycles reveal two and three peaks of light sensitivity (diapause inhibition), respectively. The first peak is 19 hours after lights-on in all regimes tested; the later peaks occlur at 24-hour intervals thereafter, providing evidence for the circadian nature of the photoperiodic clock in this insect.