Abstract: 【Aim】 To learn how the proboscis of Plutella xylostella is formed by two galeae using the dorsal and ventral linkages. 【Methods】 The mouthpart characteristics of P. xylostella were observed under light microscope. The ultrastructure of the dorsal linkage, ventral linkage and food canal of proboscis were observed under scanning electron microscope. 【Results】 The mouthparts of P. xylostella consist of a pair of labial palpi, and a proboscis is located in the middle. The proboscis is linked by two extended galeae. The dorsal linkage of proboscis is formed by overlapping lance-shaped plates of galea. The dorsal linkage contains two parts, i.e., upper and lower lanceshaped plates. In the apical part of proboscis, the lower lance-shaped plates disappear slowly while the upper lance-shaped plates gradually become larger and a row of triangular process appears in the outside. There are also some pores between upper lance-shaped plates and galea. The dorsal linkage is affected by a series of overlapping distally directed upper and lower lanceshaped plates of cuticle. However, in the subapical part of proboscis, the linkage is formed by the overlapping of the upper lance-shaped plates. The ventral linkage is affected by a series of closely applied, curved, toothed hooks which lock into each other from the two sides. Each toothed hook contains upper branch and lower branch with similar shape, the former being longer than the latter. From the basal part to the apical part of the proboscis, the length of the toothed hook gradually increases. There is a gap between the two branches for the opposite side of the toothed hook inserted. 【Conclusion】 The difference in the structure and linking mode of the dorsal and ventral linkage of the proboscis of P. xylostella may be related to the movement mode of proboscis when it coils or stretches. In the apical part of proboscis, the pores between the dorsal linkage and galea may be the place where food can be sucked in.

Key words: Plutella xylostella, galeae, proboscis, linkage, mouthpart, ultrastructure, scanning electron microscope, light microscope