Effects of photoperiod and light intensity on wing dimorphism and development in the parasitoid Sclerodermus pupariae (Hymenoptera: Bethylidae)

Abstract

Sclerodermus pupariae Yang et Yao (Hymenoptera: Bethylidae), a newly described ectoparasitoid, has been used as a biocontrol agent against several buprestid and cerambycid pests in China. Both winged and wingless female morphs of S. pupariae can find and parasitize hosts; however, winged parasitoids can disperse faster and further to new habitats and thus are more adapted to spatial and temporal changes in host densities than wingless morphs. In the present study, we determined the effects of photoperiod and associated light intensity on the parasitoid development time from egg to adult, the proportion of winged females, fecundity, and progeny sex ratio. Significantly more winged female parasitoid progeny were produced with long-day photoperiods and high light intensity compared to short day-photoperiods and low light intensity treatments. Photoperiod alone (regardless of light intensity) has significant impact on developmental time of parasitoid progeny. Light intensity, interacted with photoperiod, significantly affected the degree of phenotypic partitioning and development time, but light intensity and photoperiod did not significantly influence the parasitoid fecundity and sex ratio. These results are relevant to laboratory rearing of S. pupariae when the optimal light conditions are needed to produce winged female parasitoids.