The influence of host species and location in the host detection ability of tiphiid (Hymenoptera: Tiphiidae) parasitoids

Tiphia vernalis Rohwer and T. popilliavora Rohwer are ectoparasitoids of root-feeding larvae of the Japanese beetle, Popillia japonica Newman, and oriental beetles, Anomala orientalis Waterhouse (Coleoptera: Scarabaeidae). Little is known about the influence of host species and location in the host detection ability of tiphiid wasps. In this study we examined the response of female T. popilliavora wasps, an under-studied Tiphia species, to potential host stimuli using dual choice tests in an observation chamber filled with soil. T. popilliavora wasps were able to successfully discriminate the trails containing body odor or frass of P. japonica grubs from trails without cues. Frass trails of P. japonica grubs elicited stronger responses than body odor trails. We also examined the preference of host cues by tiphiid wasps using dual choice behavioral assays. Both T. vernalis and T. popilliavora wasps did not show preference towards trails that either contained P. japonica or A. orientalis cues. In addition, we also determined the detection of host cues by tiphiid wasps in a dual-choice test for cues presented at varying soil depths. Wasps were able to successfully discriminate between the Y-tube arms with and without cues when the cues of P. japonica were buried at a depth of 2 cm. In contrast, both Tiphia species were unable to distinguish between the Y-tube arms with and without cues when the cues were buried at a depth of 5 cm. Thus, our findings suggest that once Tiphia wasps land on the ground, they can detect the presence of their specific hosts, just below the soil surface by exploiting the kairomones present in grub body odor trails and frass and once the wasps are in the soil, they use the same cues to direct themselves to the host grubs.