FACTORS AFFECTING DIAPAUSE DEVELOPMENT AND SURVIVAL IN THE PUPA OF MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE)

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Abstract
Only soil temperatures below −7°C are likely to cause significant pupal mortality of M. configurata in the field, and only if exposure periods are sufficiently prolonged. At −17°C, a temperature not uncommonly encountered in the soil at 10 cm during the prairie winter, near total mortality occurred within 1 week in laboratory tests and significant mortality (20–30%) occurred within 1 day. The survival time at −12°C was considerably longer, and 50% mortality occurred after about 6 weeks of exposure. Pupal mortality caused by cold might thus vary from 0 to 100% depending on local climatic and field conditions and therefore is an essential component of a survival model for the species. Exposure to cold accelerates diapause development by as much as four orders of magnitude for the lowest temperature tested (−17°C). However, the acceleration of diapause development by sub-zero temperatures appears to be of limited phenological significance, since in western Canada the pupae spend at least 40 weeks in the soil and can easily complete diapause development within this time at 0° to 5°C. Further evidence for a major reorganization of the endocrine system of M. configurata pupae during stage 2 of diapause development is presented.