Morphology, Distribution and Sexual Dimorphism of Sensilla in the Tea Leaf Beetle Basilepta melanopus (Coleoptera: Eumolpidae)

The tea leaf beetle Basilepta melanopus is a devastating leaf-feeding pest of tea plants, with its infestation area and damage severity in Chinese tea plantations continuously increasing. Characterizing the morphology and distribution of sensilla provides a morphological basis for understanding the behavioral mechanisms underlying host recognition, mate localization, and environmental perception of this pest. In this study, the morphology, ultrastructural characteristics, distribution and sexual dimorphism of sensilla on antennae, mouthparts, legs, and external genitalia of B. melanopus adults were examined by stereomicroscopy and scanning electron microscopy (SEM). Nine types and thirty-nine subtypes of sensilla were observed. These include various types on the antennae, including Böhm bristles, sensilla chaetica, sensilla trichodea, sensilla basiconica, sensilla auricillica, sensilla coeloconica, and sensillar pits, and many subtypes. The two types of sensilla unique to the mouthparts are sensilla styloconica and sensilla campaniformia. Sensilla chaetica and sensilla trichodea are also found on the tarsi. In addition, sensilla trichodea and sensilla basiconica were identified on the external genitalia of the female insect. On the male external genitalia, four types of sensilla were observed: sensilla trichodea, sensilla chaetica, sensilla basiconica, and sensilla coeloconica. There were also differences in the number and size of sensilla between males and females. This study investigated the relationship between the sensilla of B. melanopus and its key behavioral activities, namely feeding and oviposition, through detailed morphological observations and systematic analysis of these sensory structures. The findings provide a conceptual framework and offer novel perspectives for future research on the behavioral ecology and integrated management of this species.