EFFECTS OF PRE-STORAGE TREATMENT ON SURVIVAL OF DIAPAUSING LARVAE OF THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

Abstract At a constant temperature of 1 °C, survival of diapausing second-instar larvae of C. fumiferana (Clem.) for any given period is, to a large extent, determined by pre-storage treatment. At a pre-storage temperature of 20 °C larval survival was 80% or higher following storage periods ranging from 169 to 290 days. Survival of larvae pre-stored at 24 °C was never as high as at 20 °C, and the survival began to decrease after 225 days storage. At 28 °C this decrease had occurred before 169 days of storage. Larvae held at high pre-storage temperatures had almost normal survival when the pre-storage period was shorter. Mean time for larvae to emerge from diapause was increased by longer diapause periods and by high pre-storage temperatures. There was a corresponding decrease in larval vigour.