Fertility and Life Table Studies with Trichogramma pretiosum and T. retorridum (Hymenoptera: Trichogrammatidae)1,2

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Abstract
Studies on life and fertility tables were undertaken with Trichogramma pretiosum Riley (uniparental race) and T. retorridum Girault to explore the potential for using the intrinsic rate of natural increase (r) as a method for differentiating races and/or species of Trichogramma. The r value of the uniparental stock did not differ greatly from the corresponding value of 5 of its clones. These clones were selected on the basis of different adult longevities. However, each of these 6 values of r was consistently greater than the r of T. retorridum. Under the limited conditions of this study, there is some indication that the intrinsic rate of natural increase may be a reliable method for differentiating 2 species of Trichogramma. Other studies were conducted with T. pretiosum to determine the repeatability of r and of its component variables. Variation in mean fertility of T. pretiosum was not significant when host eggs were presented to females 1 day old or younger. However, the mean fertility of this parasite decreased significantly if females did not have the opportunity to lay eggs in the 1st 2 days. Adult fertility varied greatly within the uniparental race of T. pretiosum. The mean fertility of the parental line was significantly lower than that of any one of its 5 clones tested. Significantly high variation in mean fertility was also found between the 5 clones. A high adult density corresponded to a low mean fertility of the progeny, and vice versa.

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