Below-ground host location by Campsomeriella annulata (Hymenoptera : Scoliidae), a parasitoid of scarabaeid grubs

Scoliid wasps are ectoparasitoids that attack soil-dwelling scarabaeid larvae, and little is known about their host-searching behavior. In this study we investigated the cues used in host location by Campsomeriella annulata (Fabricius) and examined whether or not these wasps can detect hosts in the soil from the surface. In a dual-choice test with a Y-tube, female wasps were attracted to sand with host odor, sand with host feces, and sand used for rearing the host, the larvae of Anomala rufocuprea Motschulsky (Coleoptera: Scarabaeidae). In a dual-choice test for cues presented at a distance, the wasps did not discriminate between the Y-tube arms with and without cues. In an experimental arena in which host products and a host grub were buried 0.5 cm below the surface the wasps did not respond to the cues from the surface in terms of the burrowing frequencies and antennal tapping rates. Our results indicate that C. annulata searches for the host grubs by using kairomones, residual cuticular substances, or feces deposited in the soil as the grubs move through it, and that wasps cannot perceive the host in the soil from the surface. We discuss how scoliid wasps search for soil-dwelling hosts using cues that are reliable but not highly detectable.