Influence of natal host and oviposition experience on sex allocation in a solitary egg parasitoid, Anastatus disparis (Hymenoptera, Eupelmidae)

Constraints on adaptation are a major topic in evolutionary biology. Sex allocation, in particular the ratio of the sexes, has often been used as a key process for studying constraints on adaptation. Anastatus disparis Ruschka (Hymenoptera: Eupelmidae) is a solitary egg parasitoid of gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), and several other lepidopteran forest pests. Here, we compared two different sized substitute hosts, the smaller one Dictyoploca japonica Moore (Lepidoptera: Saturnidae) and the larger one Antheraea pernyi Guerin-Meneville (Lepidoptera: Saturnidae), and investigated the influence of natal host and oviposition experience on sex allocation by A. disparis. Results showed that natal host had almost no impact on sex allocation by A. disparis, but oviposition experience did influence sex allocation of A. disparis on D. japonica eggs. This suggests that information females obtain from the environment influences how they allocate sex in their offspring. However, the sex ratios of A. disparis emerging from A. pernyi eggs were consistent irrespective of oviposition experience of female A. disparis. This indicates that the eggs of A. pernyi are large enough to maximize female progeny of A. disparis.