Oviposition behavior in the robber fly Mallaphora ruficauda (Diptera: Asilidae)

Mallophora ruficauda Wiedemann (Diptera: Asilidae) is a pestiferous robber fly affecting beekeeping in the South American open grasslands. This insect preys upon other insects during its adult stage and parasitizes scarab beetle larva in the soil as larvae. As a first step toward population management, we studied basic reproductive behavioral traits. We investigated the size and fertility of egg clusters and whether females exhibit preferences for oviposition sites. We collected egg clusters close to bee farms in the Argentine grasslands and estimated egg eclosion rates and aggregation. We also measured the height at which clusters were found on both natural vegetation and artificial wire supports. We determined the number of eggs per egg cluster, eclosion rates, and egg developmental time. Egg clusters were usually highly aggregated in the field and were found on elevated places, including the tallest plant species. We discuss height selectivity in robber flies in relation to host availability and robber fly fecundity, as a means of increasing larval dispersal and hence encountering success with larval hosts.