Canadian Forest Service Publications
Diapause termination and changes in thermal responses during postdiapause development in larvae of the spruce budworm, Choristoneura fumiferana. 1990. Régnière, J. Journal of Insect Physiology 36: 727-735.
Available from: Laurentian Forestry Centre
Catalog ID: 14204
CFS Availability: PDF (request by e-mail)
Diapause termination was examined in field-overwintering populations of the spruce budworm, Choristoneura fumiferana (Clem.). The time required for emergence of overwintering larvae decreased rapidly until the end of December following which photoperiod had no effect on diapause termination. There was no detectable yearly or geographical variation in the duration of postdiapause development, or in its relationship with temperature, when measured in early March. Thus, it is concluded that diapause in this species ends before the end of February. Cycling temperatures led to slower development than expected from temperature responses of the overwintering larvae, suggesting developmental inertia to temperature flutuations. There was a brief but pronounced increase in developmental rate in the first few days after transfer from the field to experimental conditions. Sensitivity of overwintered larvae to warm temperature increased gradually during postdiapause. This is hypothesized as a mechanism by which adequate synchrony is achieved between the emergence of larvae from diapause, the appearance of suitable food, and optimal weather conditions for the establishment of young larvae on host-tree foliage. A method was developed to incorporate age-dependence in mathematical descriptions of relationships between temperature and development rates for the purposes of simulation.
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