Effects of female mating status and age on fecundity, longevity and sex ratio in Trichogramma minutum (Hymenoptera: Trichogrammatidae)
Abstract
Effects of female mating status and age of Trichogramma minutum Riley on its fecundity, longevity and offspring sex ratio were detennined in the laboratory, using eggs of the variegated cutworm as hosts. Although the mating status of female T. minutum did not affect their total fecundity significantly (P > 0.05), mated and unmated females showed different allocations of progeny. Mated females deposited significantly more eggs (P < 0.05) than those unmated on the first day of exposure to hosts. On subsequent days, however, unmated females parasitized significantly more hosts (P < 0.05) than those mated. Mated females laid 82.4% of their total fecundity on the first day of oviposition, whereas unmated females laid 58.3%. The number of eggs parasitized by both groups of females decreased significantly (P < 0.05) with parasitoid age. Unmated females lived longer (P < 0.05) than their mated counterparts. No significant differences (P> 0.05) in clutch size (the number of parasitoid offspring produced per parasitized host) and emergence rate were found between the offspring of mated and unmated female parasitoids. The sex ratio of the offspring of mated females changed significantly (P < 0.05) with maternal age: younger females produced a higher proportion of daughters than did older parasitoids. Unmated females produced male offspring only.
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