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ECOLOGICAL OBSERVATIONS ON CHRYSOCHARIS LARICINELLAE (HYMENOPTERA: EULOPHIDAE), A PARASITE OF THE LARCH CASEBEARER (COLEOPHORA LARICELLA)

Published online by Cambridge University Press:  31 May 2012

F. W. Quednau
F. W. Quednau
Affiliation:
Forest Research Laboratory, Department of Forestry and Rural Development, Quebec, Quebec
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Abstract

An account is given of host acceptance, the influence of temperature on fecundity and longevity, and searching capacity of Chrysocharis laricinellae (Raczeburg), a parasite of the larch casebearer, Coleophora laricella (Hübner).

Fourth-instar case-bearing larvae were the preferred stages for attack. The size of the parasite progeny varied directly with the size of the host. Fecundity of progeny reared from small hosts was significantly less than that of progeny reared from large hosts. Not all parasite adults could successfully oviposit through the tough skin of the host pupa. C. laricinellae showed poor searching capacity. Superparasitism was common at low host densities of the casebearer and resulted in either one parasite emerging or in total parasite mortality. A sex ratio where females predominated resulted when sufficient numbers of preferred stages of the host were presented to mated C. laricinellae. The temperature threshold for attacking hosts was 55°F, and for development of the parasite 40°F. At 50°F the adults lived 4 months on the average.

Therefore C. laricinellae is able to survive in the field without alternate hosts and at very low host densities. The parasite seems to depend on a continuing supply of suitable instars of host species in sufficient numbers to be effective. If C. laricella is the only available host species in the ecosystem the biological control value of this chalcid must be rated as poor.

Résumé

Rapport sur la réceptivité de l'hôre vis-à-vis Chrysocharis laricinellae (Ratzeburg), la fécondité et la longévité de ce parasite en relation avec la température, et sa capacité à trouver son hôte, le Porte-case du mélèze, Coleophora laricella (Hübner). Le parasite préfère attaquer les larves du quatrième âge dans leur case. La taille et la fécondité de la progéniture du parasite est directement proportionnelle à la taille de l'hôte. Quelques patasites adultes ne réussissent pas à déposer leurs oeufs à travers la peau de la pupe de C. laricella. En général, le parasite montre peu de facilité à ttouver son hôte. Le superparasitisme est assez commun dans les populations de faible densité du porte-case et donne lieu à une mortalité complète ou à la sortie d'un seul parasite. Des femelles de C. laricinellae fécondées et mises en présence de larves du quatrième âge en nombre suffisant, donnèrent une progéniture à prédominance de femelles.

Le seuil de développement du parasite se situe à 40°F, et celui de l'attaque de son hôte à 55°F. La longévité de l'adulte de C. laricinellae est de 4 mois en moyenne à 50°F. Ainsi C. laricinellae peut survivre sans hôtes secondaires et à de faibles densités de population de l'hôte. Pour être effectif, le parasite semble dépendre d'une présence constante d'espèces d'hôte d'âges convenables. Si C. laricella est le seul hôte disponible dans l'écosystème, la valeur de ce chalcidien comme facteur de répression doit être estimée comme peu importante.

Type
Articles
Information
The Canadian Entomologist , Volume 99 , Issue 6 , June 1967 , pp. 631 - 641
Copyright
Copyright © Entomological Society of Canada 1967

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