Behavioural and genetic approaches to evaluate the effectiveness of deterrent marking by a parasitoid wasp

Some parasitoids deposit chemical signals after oviposition as an indication that the host has already been parasitized. This marking can deter subsequent conspecifics or one’s self from laying eggs in previously exploited hosts, thus reducing the risk of superparasitism. We investigated the egg laying behaviour of the parasitoid wasp Hyposoter horticola. In a laboratory experiment, we tested whether oviposition, post-oviposition marking, or both together deter subsequent oviposition by conspecifics. We then tested the effectiveness of the deterring mark under natural conditions using maternity assignment based on 14 polymorphic DNA microsatellite markers. The behavioural experiment showed that patch marking deters conspecifics from probing the host eggs, and oviposition deters those that probe from laying eggs in previously parasitized host clusters. These results were confirmed by the maternity assignment showing that under natural conditions, host egg clusters are primarily parasitized by a single H. horticola female.