Fine Morphology of the Proboscis and Associated Sensilla in Pontia edusa (Fabricius, 1777) (Lepidoptera: Pieridae)

Pontia edusa is a nectar-feeding butterfly widely distributed in Europe, northwestern India, Siberia, North Africa (extending to Ethiopia), and most regions of China; however, detailed information on the fine morphology of its proboscis remains limited. In this study, scanning electron microscopy was used to examine the external morphology, zonal organization, and sensilla composition of the adult proboscis, and sexual differences in selected morphological parameters were statistically analyzed. The proboscis consists of a pair of elongated maxillary galeae that interlock via dorsal and ventral legulae to form a continuous food canal. Based on structural variation in the dorsal legulae, the proboscis can be divided into three zones. Zone 1 is characterized by tightly interlocked legulae and serrated external ridges; Zone 2 shows enlarged interlegular gaps and gradual modification of external surface ornamentation; and Zone 3 lacks dorsal legulae and bears flake-like bumps. Three major types of sensilla were identified on the proboscis, including sensilla chaetica, basiconica, and styloconica, comprising six subtypes in total. The sensilla chaetica subtype sc2, restricted to the ventral surface of the proximal proboscis, represents a previously unreported morphological feature for P. edusa. These results provide a detailed morphological framework for the proboscis of P. edusa and expand the comparative basis for evaluating structural diversity and regionalization patterns of the proboscis in flower-visiting pierid butterflies.