Dual photoperiodic regulation to enable univoltine life cycle in alpine silver-Y moth, Syngrapha ottolenguii (Noctuidae: Plusiinae) without obligatory diapause

Abstract

Syngrapha ottolenguii (Noctuidae: Plusiinae) is a typical Japanese alpine moth with adults appearing from mid to late summer. Field and laboratory studies show that this species has a univoltine cycle in 1 year, although one generation can be completed in 60 days at 16L-8D and 20°C. We found two strategies - short-day-induced prolongation of 2nd and 3rd instar larval stages for winter, and long-day-induced arrestment of reproductive maturation in adults for summer to enable the univoltine life history without obligatory diapause in the severe alpine climate. As a result, oviposition is delayed into autumn, and the late-hatching, cold-tolerant larvae overwinter under deep snow. Larvae before and after overwintering develop very slowly due to their unique behavior of hiding from the sun's radiant heat.