Decreasing Photoperiod inhibiting Metamorphosis in an Insect

Abstract

Anthrenus verbasci (L.) (Col. Dermestidae) has a two-year life-cycle (semivoltine) under outdoor temperature conditions in southern England, spending the first winter as a young larva and the second as a fully grown larva¹. Under constant conditions in the laboratory larvæ may be either uni- or semivoltine according to temperature. The percentage of larvæ with a univoltine life-cycle increases from 0 at 15° C. to 100 at 25° C. The larvæ have been shown to possess an endogenous and persistent rhythm controlling the onset of diapause². Each cycle of the rhythm consists of a period of active growth (with moulting and/or pupation) followed by diapause. Under constant conditions the length of the cycle is about 44 weeks, but this is extended to an annual cycle, under outdoor conditions, by the insertion of a period of dormancy after the completion of diapause.