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FACTORS AFFECTING LARVAL DIAPAUSE IN DENDROCTONUS RUFIPENNIS (COLEOPTERA: SCOLYTIDAE)

Published online by Cambridge University Press:  31 May 2012

E.D.A. Dyer  and
P.M. Hall
E.D.A. Dyer
Affiliation:
Pacific Forest Research Centre, Canadian Forestry Service, Victoria, British Columbia V8Z 1M5
P.M. Hall
Affiliation:
Pacific Forest Research Centre, Canadian Forestry Service, Victoria, British Columbia V8Z 1M5
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Abstract

The effect of daily day-degrees C in relation to brood age was investigated to determine its influence on the induction of larval (prepupal) diapause in Dendroctonus rufipennis (Kirby). Daily day-degrees of less than about 9° above the development threshold (6.1°C) induced diapause in most of the broods while diapause was averted by daily day-degrees C of 10 or more above the threshold. Induction of diapause occurred no later than third larval instar; temperature changes during the fourth instar produced no change in aversion or induction of diapause. Laboratory results reveal that field temperatures during larval development determine whether most beetles have a 1- or 2-year life cycle.

Résumé

On a étudié l’effet des degrés-jours (°C) par jour en relation avec l’âge d’incubation pour déterminer son influence sur l’induction de diapause larvaire (prénymphale) As Dendroctonus rufipennis (Kirby). Des degrés-jours quotidiens de moins de 9° environ au-dessu du seuil de développement (6.1°C) ont produit une diapause partielle ou complète alors que presque toute diapause fut écartée par des degrés-jours (°C) par jour de 10° ou plus au dessus du seuil. La diapause fut déclenchée pas plus tard qu’au troisième stade larvaire; les changements de température au cours du quatrième stade n’on produit aucun changement dans l’empêchement ou dans l’induction de la diapause. Des résultats en laboratoire révèlent que les températures sur le terrain durant le développement des larves déterminent si la plupart des dendroctones auront un cycle biologique de 1 ou 2 ans.

Type
Articles
Information
The Canadian Entomologist , Volume 109 , Issue 11 , November 1977 , pp. 1485 - 1490
Copyright
Copyright © Entomological Society of Canada 1977

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