Many researchers have evaluated fitness parameters under laboratory conditions to predict the performance of Trichogramma in the field. However, there have been few attempts to assess such fitness measures under field conditions. This study investigates the effects of variation in wing size and wing shape on the field fitness of the egg parasitoid Trichogramma carverae Oatman and Pinto (Hymenoptera: Trichogrammatidae). A genetically heterogeneous strain of this wasp was released in Chardonnay vines and individual females were recaptured on eggs of the light brown apple moth, Epiphyas postvittana Walker (Lepidoptera: Tortricidae).
Females that located host eggs in the field were compared to a random sample of females from the release population. Landmarks were identified on digitized images of mounted wasps and wing size was measured as the centroid size computed from the inter landmark distances. Procrustes superimposition methods eliminated size variation to allow wing shape to be assessed. Principal component analysis of the residual landmarks identified several factors contributing to shape changes. The analyses suggested that field fitness was linearly related to wing size and three wing shape dimensions, one of which did not show an allometric relationship.
Another experiment, conducted under laboratory conditions, showed that female wing size was correlated with host egg volume, although this factor only accounted for 12% of the size variance. These findings suggest that both size and shape can be correlated to field performance in T. carverae and that these measures may help to develop practical indicators of wasp quality.
Species 1: Hymenoptera Trichogrammatidae Trichogramma carverae (Trichogramma)
Species 2: Lepidoptera Tortricidae Epiphyas postvittana (Light brown apple moth)
Species 3: Lepidoptera Gelechiidae Sitotroga cerealella (Angoumois grain moth)
Keywords: parasitoid, centroid
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