Effects of vitamin E concentrations on sex ratio of Pimpla turionellae (Hymenoptera: Ichneumonidae) adults

We report here the effects of vitamin E concentrations (0.0010%, 0.0015% and 0.0020%) in artificial diets on adult emergence and sex ratios of emerging adults of the parasitic wasp, Pimpla turionellae L. (Hymenoptera: Ichneumonidae). We found that average adult emergence was not affected by the absence or presence of vitamin E at the concentrations tested in the diet. However, the sex ratio differed significantly from a 1:1 ratio, favoring females, Lit 0.0010% and 0.0015%. A maximum of 65.63% females occurred at the 0.0015% level. When emergence and sex ratio data were viewed on aperiodic basis between 10 and 34 d of age of the parasitizing parental females, considerable variation occurred but did not obscure the overall results. The dramatic decrease in the percentage of females emerging in the control and 0.0020% groups beginning on day 19 explains why the overall sex ratio in these two groups did not differ from 1:1. The only additional trend was an apparent decrease in adult emergence toward the end of the experimental period at the 0.0020% level.