Abstract:  【Aim】 This study aims to characterize the morphology of sensilla on proboscis and the central projection of their sensory neurons in adults of the diamondback moth, Plutella xylostella. 【Methods】 The structure of the proboscis of P. xylostella adults and sensilla on the proboscis were observed under scanning electron microscopy, and the central projection of the sensory neurons of sensilla on the proboscis were observed by using neuronal backfills and confocal microscope. 【Results】 Five types of sensilla were found on the proboscis, including sensilla trichodea (two subtypes), sensilla coeloconica, sensilla basiconica, sensilla chaetica and sensilla styloconica. Sensilla trichodea are located outside of each galea with a smooth surface, and can also be divided into two subtypes (sensilla trichodea subtype Ⅰ and Ⅱ), of which subtype Ⅰ is longer than subtype Ⅱ. Sensilla basiconica are located outside of the proboscis, and composed of a sensory cone and short dome-shaped socket. Sensilla coeloconica have a sensory cone but no socket, and only occur in the food canal. Sensilla chaetica are composed of a long sensory bristle and a round socket, without pores on the surface, and occur on the external surface of the proboscis. Sensilla styloconica are the most typical sensilla on the proboscis, consisting of a single sensory cone inserted at the top of a stylus, and concentrated in the tip region. The sensory and motor neurons on the proboscis project to the primary gustatory center, the suboesophageal ganglion (SOG). 【Conclusion】 The types, distribution and morphology of sensilla of the proboscis of P. xylostella adults and the pattern of central projections of their neurons have been illustrated in this study, providing a basis for further investigation on the physiology and function of sensilla of the proboscis of P. xylostella．

Key words: Plutella xylostella, proboscis, sensilla, nerve projection, ultrastructure