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THE DIAPAUSE RESPONSE TO PHOTOPERIOD IN ONTARIO POPULATIONS OF COTESIA MELANOSCELA (RATZEBURG) (HYMENOPTERA: BRACONIDAE)

Published online by Cambridge University Press:  31 May 2012

V.G. Nealis ,
D. Oliver  and
D. Tchir
V.G. Nealis
Affiliation:
Canadian Forest Service-Sault Ste. Marie, PO Box 490, Sault Ste. Marie,Ontario, Canada P6A 5M7
D. Oliver
Affiliation:
Canadian Forest Service-Sault Ste. Marie, PO Box 490, Sault Ste. Marie,Ontario, Canada P6A 5M7
D. Tchir
Affiliation:
Canadian Forest Service-Sault Ste. Marie, PO Box 490, Sault Ste. Marie,Ontario, Canada P6A 5M7
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Abstract

The diapause response to photoperiod in Ontario populations of Cotesia melanoscela, an introduced parasitoid of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), was investigated under a series of stationary photoperiods and constant temperature. When the parasitic larval stages of C. melanoscela were exposed to different photoperiods, the insect exhibited a typical long-day response: long days (greater than 18 h) promoted continuous development whereas short days (less than 16 h) resulted in diapause in the cocooned prepupal stage. Within the region of the critical photoperiod (16–18 h) the diapause response was associated with larval development time. Individuals that developed more slowly were more likely to enter diapause. Cotesia melanoscela was sensitive to photoperiod throughout its entire larval period. These individual responses are used to interpret patterns of seasonality of the parasitoid in Ontario and to compare with published information from populations of C. melanoscela in New England.

Résumé

L’influence de la photopériode sur la diapause au sein des populations ontariennes de Cotesia melanoscela, un parasotoïde introduit de la Spongieuse, Lymantria dispar (L.) (Lepidoptera : Lymantriidae), a fait l’objet d’une étude dans une série de conditions constantes de photopériode et de température. Lorsque les larves de C. melanoscela sont exposées à différentes photopériodes au cours de leurs stades parasites, l’insecte réagit comme il le fait dans des conditions de jours longs : les jours longs (plus de 18 h) favorisent le développement continu, alors que les jours courts (moins de 16 h) déclenchent le diapause des larves de stade pré-nymphe dans leur cocon. Près du seuil critique (photopériode de 16 à 18 h), le déclenchement de la diapause est relié à la vitesse du développement larvaire : les individus à développement lent sont plus susceptibles d’entrer en diapause. Cotesia melanoscela est sensible à la photopériode durant toute la durée de son développement larvaire. Ces variations individuelles sont utilisées ici pour interpréter les aspects saisonniers de la biologie du parasitoïde en Ontario et elles sont comparées aux données publiées sur les populations de C. melanoscela de Nouvelle-Angleterre.

[Traduit par la Rédaction]

Type
Articles
Information
The Canadian Entomologist , Volume 128 , Issue 1 , February 1996 , pp. 41 - 46
Copyright
Copyright © Entomological Society of Canada 1996

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