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DEVELOPMENT AND SURVIVAL OF AXENICALLY REARED MOUNTAIN PINE BEETLES, DENDROCTONUS PONDEROSAE (COLEOPTERA: SCOLYTIDAE), AT CONSTANT TEMPERATURES

Published online by Cambridge University Press:  31 May 2012

L. Safranyik
Affiliation:
Canadian Forestry Service, Pacific Forest Research Centre, Victoria, British Columbia V8Z 1M5
H. S. Whitney
Affiliation:
Canadian Forestry Service, Pacific Forest Research Centre, Victoria, British Columbia V8Z 1M5

Abstract

The development and survival of mountain pine beetles axenically reared on standardized diet at 8 constant temperatures (10°–35 °C) were observed. At 32 °and 35 °C, 22 and 18% of the eggs hatched and all larvae died within 10 d of hatching. At the lower temperatures, 60–70% of the eggs hatched. The highest survival for all developmental stages was at 24 °C. At 10° and 15 °C development of all beetles reared in bolts of lodgepole pine or on axenic diet stopped when larvae were fully developed, whereas at 24 °and 27 °C all of the beetles developed normally to the adult stage. Larvae that had stopped developing during rearing at 15 °C resumed development after being transferred to 24 °C, indicating that pupation was limited by temperature. Although mean development times to the larval, pupal, and adult stages all decreased with increasing incubation temperature, heat-unit requirements above a base temperature of 5.6 °C were lowest for individuals reared at 27 °and 24 °C for all developmental stages. At these temperatures, an estimated average of 673 and 674 degree-days above 5.6 °C were required for development from egg to the tanned (dark) adult stage, respectively. The average widths of the prothorax and the sex ratios of axenic beetles were within published ranges. Mean development times and heat-unit requirements at constant temperatures for development to various life stages agreed well with published field and laboratory studies from western Canada.

Résumé

Les auteurs ont étudié le développement et la survie de dendroctones du pin ponderosa élevés en axénie sur milieu normalisé à huit températures maintenues constantes (intervalle de 10° à 35 °C). A 32 °et 35 °C, 22 et 18% des oeufs ont éclos, mais toutes les larves sont mortes dans les 10 jours suivant l'éclosion. Aux températures plus basses, 60 à 70% des oeufs ont éclos. Pour tous les stades de développement, le taux de survie a été maximal à 24 °C. A 10° et 15 °C, le développement, de tous les dendroctones élevés sur des billes de pin tordu ou sur un milieu aseptique s'est arrêté à la fin de la phase larvaire, tandis qu'à 24 °et 27 °C, tous les dendroctones se sont développés normalement jusqu'au stade adulte. Les larves qui avaient arrêté de se développer à 15 °C ont repris leur développement lorsqu'elles ont été placées dans un environnement à 24 °C, ce qui indique que la nymphose était limitée par la température. Même si les temps moyens de développement jusqu'aux états larvaire, nymphal et adulte diminuaient tous trois plus la température d'incubation était élevée c'est pour les individus élevés à 27 °et 24 °C que les besoins thermiques au-dessus d'une température de référence de 5.6 °C ont été les plus faibles pour tous les stades de développement sauf l'oeuf. On a estimé qu'à 24 °C, il fallait en moyenne 673 degrés-jours au-dessus de 5.6 °C pour le développement de l'oeuf jusqu'au stade adulte de teinte foncées. Les largeurs moyennes du prothorax et les rapports des sexes des dendroctones axéniques se trouvent dans la gamme des valeurs publiées. Les temps moyens de développement et les exigences thermiques pour le développement jusqu'à divers stades correspondent bien aux valeurs publiées obtenues lors d'études sur le tarrain et en laboratoire dans l'ouest canadien.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1985

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