Morphology and distribution of sensilla on the antennae and ovipositor of the Hymenopteran parasitoid Pseudotorymus jaapiellae Yang et Chen

Abstract

Pseudotorymus jaapiellae is an important ectoparasitoid of the larvae of Gephyraulus lycantha, a serious gall-forming pest that devastates wolfberry, Lycium barbarum, in Northwest China. To provide requisite background for our ongoing research on the mechanisms of P. jaapiellae's host location and subsequent oviposition, we used scanning electron microscopy to describe the external morphologies and distributions of sensilla on their antennae and ovipositors. The geniculate antennae of both male and female P. jaapiellae were each composed of a scape with a basal radiculum, a pedicel, an anellum and a flagellum. We identified nine morphological sensilla types on the antennae of both sexes, including three sensilla trichodea (ST), one sensillum basiconicum (SB), two sensilla chaetica (SCh), one sensillum placodeum (SP), one sensillum coeloconicum (SCo), and one sensillum campaniformia (SCa). Females had significantly more ST I and SP than males had, but males had more ST III than did females. We observed six types of sensilla on the ovipositor, including three ST, one SB, and two SCa. ST II, ST IV and SB II were on the sheath, whereas ST V and the SCa were on the stylus. Finally, the possible biological functions of these sensilla were discussed according to their morphology and ultrastructure. These results provide an important basis for further study on chemical communication between P. jaapiellae and their host, and contribute to the development of a biological control program for G. lycantha, using the parasitoid, P. jaapiellae.