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SIZE DIFFERENCES OF LABORATORY REARED AND WILD POPULATIONS OF TRICHOGRAMMA MINUTUM (HYMENOPTERA: TRICHOGRAMMATIDAE)1

Published online by Cambridge University Press:  31 May 2012

Susan G. Southard ,
Mark W. Houseweart ,
Daniel T. Jennings  and
William A. Halteman
Susan G. Southard
Affiliation:
Cooperative Forestry Research Unit, School of Forest Resources, University of Maine at Orono 04469
Mark W. Houseweart
Affiliation:
Cooperative Forestry Research Unit, School of Forest Resources, University of Maine at Orono 04469
Daniel T. Jennings
Affiliation:
Northeastern Forest Experiment Station, USDA Building, University of Maine at Orono 04469
William A. Halteman
Affiliation:
Deptartment of Mathematics, University of Maine at Orono 04469
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Abstract

Three body dimensions (body length, head width, and abdomen width) were used to determine size differences between laboratory-reared and wild populations of Trichogramma minutum Riley. Six separate groups of T. minutum were measured: three groups were from Sitotroga cerealella (Olivier) eggs, two from spruce budworm Choristoneura fumiferana (Clemens) eggs, and one from wild populations of spruce budworm.

Female T. minutum from spruce budworm (large host) eggs were significantly larger for all body dimensions than T. minutum from S. cerealella (small host) eggs. Male T. minutum from field-collected spruce budworm eggs were significantly larger for all body dimensions than T. minutum reared for more than one generation in S. cerealella eggs.

A significant reduction in female parasitoid size was observed during the initial generations of T. minutum reared in the smaller host (S. cerealella). However, this size reduction was not permanent. Following numerous generations in the S. cerealella host eggs, a significant increase in female parasitoid size was noted within the first generation of T. minutum reared in the spruce budworm host eggs.

Résumé

Trois dimensions corporelles (longueur du corps, largeur de la tête, et largeur de l'abdomen) ont été utilisées pour examiner les différences de taille entre des populations de laboratoire et des populations naturelles de Trichogramma minutum Riley. Six groupes différents de T. minutum ont été mesurés : 3 groupes provenaient d'oeufs de Sitotroga cerealella (Olivier), deux provenaient d'oeufs de la tordeuse des bourgeons de l'épinette, Choristoneura fumiferana (Clemens), et le troisième d'une population naturelle de la tordeuse.

Les femelles de T. minutum provenant d'oeufs de tordeuse (hôte le plus gros) étaient de taille significativement plus grande que celles provenant d'oeufs de S. cerealella (hôte le plus petit), d'après les 3 dimensions mesurées. Les mâles de T. minutum provenant d'oeufs de tordeuse recueillis sur le terrain étaient significativement plus grands, pour les 3 mesures utilisées, que ceux élevés depuis plus d'une génération sur des oeufs de S. cerealella.

Une réduction significative de la taille des femelles fut observée durant les premières générations d'élevage du parasitoïde sur l'hôte le plus petit (S. cerealella). Cependant, cette réduction n'est pas irréversible. Après plusieurs générations d'élevage sur des oeufs de S. cerealella, une augmentation significative de la taille du parasitoïde fut observée dès la première génération suite à un re-transfert sur des oeufs de tordeuse.

Type
Articles
Information
The Canadian Entomologist , Volume 114 , Issue 8 , August 1982 , pp. 693 - 698
Copyright
Copyright © Entomological Society of Canada 1982

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