Sensilla on organs of female and male Aphidius gifuensis (Hymenoptera: Aphidiidae)

Aphidius gifuensis Ashmaed parasitizes several species of aphids that cause economic damage to globally important crops; however, the mechanism of host location in this species is unclear. Here, we studied the sensory system in A. gifuensis to explore the likely mechanisms of host location that could be useful in the improved application of this species in aphid biological control programs. We used scanning electron microscopy to observe the external morphologies of the sensilla recorded from the entire body of female and male A. gifuensis. We recorded 16-18 segments and five types of sensilla on female antennae, including Bohm bristle, Chaetica sensillum, basiconic sensillum, trichoid sensillum, and placodea sensillum. The male antennae consisted of 18-20 segments, and distribution of sensilla was similar to female antennae with minor differences. No hole on the surface or tip of the sensilla was observed. Interestingly, scattered pores around the TS were found on the entire body of females, but only from the antennae, abdomen, and thoracic legs in males. TS was the most abundant and widely distributed sensillum. Tympana structures were found on antennae and femur of thoracic legs. Antenna cleaner was found on the tibia of propodeum and wing cleaner was found on the tibia of metapedes. Special crevice-shaped structures were found on the abdomen in both sexes, whereas strip-shaped structures were found only on the abdomen of females. Possible functions of the sensilla in relation to their morphologies are discussed.