Scanning electron microscopy of antennal sensilla of Megastigmus sichuanensis Doğanlar et Zheng (Hymenoptera: Torymidae)

The antennal sensory sensilla of Megastigmus sichuanensis Doğanlar et Zheng (Hymenoptera: Torymidae) were observed with scanning electron microscopy in this study. The antenna of M. sichuanensis was geniculate and the flagellum was composed of 11 subsegments. Four distinct types of sensory receptors were observed, including sensillum chaetica, sensillum trichodea, sensillum basiconica, and sensillum placodea. Two morphological subtypes of sensillum chaetica were found on the antennae, and sensillum trichodea was also divided into two morphological subtypes that were found on flagellum subsegments 2-10. Sensillum basiconica was divided into three morphological subtypes that were found on subsegments 8-10 of the flagellum, and sensillum placodea was only found on the flagellum. The shape, length, and diameter of antennae between male and female adults were similar. However, the length, diameter and number of the four distinct types of sensillum on the male were significantly greater than those of the female. The type, length, diameter, number, and distribution of these sensilla are described and their possible functions discussed. Future studies on the biology of olfaction and sexual communications in M. sichuanensis will be facilitated by these observations.