Characteristics of the larval diapause in Ctenucha virginica (Lepidoptera: Arctiidae)

Abstract

Ctenucha virginica (Esp.), a univoltine species in Québec, overwinters as a late-instar larva. Larvae brought into the laboratory between October and February and placed at 25°C under 16 h light-8 h dark, showed reduced feeding, diurnal movement, diurnal oxygen consumption, and developmental rates when compared to larvae collected in the spring. However, C. virginica displayed no seasonal variation in nocturnal metabolic rates or activity levels. Furthermore, the oxygen consumption of larvae in diapause was temperature dependent, with Q 10s varying from 2.7 (nocturnal) to 4.0 (diurnal). The ability to overwinter in any one of three larval instars may help C. virginica to synchronize its diapause initiation with the onset of low temperatures. This is especially important for C. virginica, as larvae held at 25°C under 16 h light-8 h dark during diapause died, probably due to a high metabolic rate coupled with a reduced food intake.