Larval Diapause of Maternal Origin: Induction of Diapause in Nasonia Vitripennis (Walk.) (Hymenoptera: Pteromalidae)

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Abstract
1. The environmental factors responsible for the induction of larval diapause in Nasonia vitripennis are photoperiod, temperature and host deprivation. They are effective during the life of the female parent and not during larval development. 2. Short daylength and low temperature induce females to produce diapause larvae early in reproductive life and long daylength and high temperature avert diapause. Conditions of darkness are ‘intermediate’ in this respect. The effects of daylength are reversible during the life of the female. 3. Females switch from the production of developing to diapause larvae during their reproductive life, so that a distinct age pattern is apparent. The two strains of Nasonia used in this investigation showed different patterns of diapause production. Although this difference is shown to be under ultimate genetic Control, the mechanism of induction is purely maternal and the males play no part in determining the diapause characteristics of their immediate progeny. 4. Unlike other cases of photoperiodic induction of larval diapause, the mechanism cannot operate solely through the central nervous system and a chemical ‘factor’ (a hormone?) passed from the parent female through the egg to the larva is postulated.