Digging and burying of hosts by a pupal parasitoid

Abstract

1. This study describes the host‐handling behaviour of the parasitoid Dirhinus giffardii (Silvestri) (Hymenoptera: Chalcididae). Dirhinus giffardii sometimes excavates underground hosts, parasitises them, and buries them in the soil. Considering that the parasitoid can parasitise underground hosts without excavating them, we hypothesised that the parasitoid excavates hosts to evaluate the host quality. We also hypothesised that the parasitoid buries them to reduce the risk of superparasitism because superparasitism is common in D. giffardii.2. Pupae of the oriental fruit fly Bactrocera dorsalis (Diptera: Tephritidae) were buried in or placed on peat moss as an experimental treatment, and the behavioural responses of the parasitoid towards the hosts were examined. Small and large hosts, and empty puparia were simultaneously presented to a parasitoid.3. The probability of excavation was greater for larger hosts than for smaller hosts or empty puparia. However, while it appeared that parasitoids could evaluate the size of the hosts, they did not preferentially parasitise large hosts in the soil. In addition, unusable empty hosts were readily excavated. Parasitism risk was higher for hosts located on a peat moss surface than for the buried hosts, which is consistent with the hypothesis that the hiding hosts reduces the risk of superparasitism. Alternative hypotheses for the mixed results have been discussed in the paper.