Abstract
The morphology, number, and distribution of antennal sensilla differ between males and females, reflecting adaptations to sex-specific ecological roles and life histories. In this study, scanning electron microscopy was employed to examine the antennal structure and sensilla types of adult males and females of Sclerodermus guani Xiao et Wu 1983 (Hymenoptera: Bethylidae), with a focus on identifying morphological differences between the sexes. The results revealed that the antennae of both sexes are geniculate; however, female antennae are shorter and broader than those of males. Each antenna comprises 13 segments, including a scape (1 segment), a pedicel (1 segment), and a flagellum (11 segments). Eight distinct types of sensilla were identified on the antennae of both males and females, with notable sex-specific differences in sensilla types and subtypes. Trichoid sensilla subtype III was found exclusively in males, whereas long basiconic sensilla and basiconic sensilla subtype II were unique to females. More than 70% of the antennal sensilla in both sexes were olfactory in nature, highlighting their predominant role in chemical detection. The observed sexual dimorphism in the morphology and distribution of olfactory sensilla suggests functional specialization, potentially linked to host localization in females and mate location in males.