The morphological diversity of insect mouthparts is closely related to changes in food sources and diets. Research into the structures of insect mouthparts may help to establish a fundamental basis for a better understanding of insect feeding mechanisms. In this study, we examined the fine morphology of the mouthparts of Illeis chinensis using scanning electron microscopy. We paid particular attention to the types, quantities, and distribution of sensilla on the mouthparts. Our results showed that the basic components of the mouthparts of I. chinensis are the same as those in other lady beetles, i.e., the labrum, mandible, maxillae, labium, and hypopharynx. We also found structural specialization indicating adaptation to fungal feeding. On the mouthparts, there are eight kinds of sensilla and two kinds of glandular structures, including sensilla chaetica, sensilla basiconica, sensilla styloconica, sensilla coeloconica, sensilla campaniformia, sensilla placodea, sensilla digitiformia, Böhm bristles, perforated plates, and cuticular pores. This is the first time that sensilla digitiformia has been reported in ladybirds. Finally, variations in mouthparts among ladybirds with differing diets, as well as the putative functions of each of the mouthparts and sensilla, were discussed. This research can provide a reference for understanding the functions of the mouthparts in ladybird feeding behavior and thereby contribute to the development of precise insect behavior regulation and management strategies.

Mouthparts are the feeding organs of insects, which play vital roles in the feeding process. The morphology of insect mouthparts has greatly evolved according to different foods and feeding habits. Therefore, studying the structure of the mouthparts is the key to understanding their feeding mechanisms. Vibidia duodecimguttata is an important biological control agent for powdery fungus. In this study, the fine morphology of the mouthpart of V. duodecimguttata was studied by scanning electron microscopy. The basic components of mouthpart of V. duodecimguttata are similar to those of other ladybeetles, while the specific morphology of each part is different. In total, six kinds of sensilla were identified on mouthpart, and twelve types of sensilla were divided according to their morphology, length and distribution. In addition, two kinds of glandular structures were also found, namely perforated plates and cuticular pores. Finally, the morphological differences between mycetophagous and other feeding habits ladybeetles were compared, and the function of each kind of sensilla was discussed, which may establish a solid foundation for further understanding of the feeding mechanism of ladybirds.

Mouthparts are the main feeding organs of insects, which play vital roles in the feeding process. The morphology of insect mouthparts has greatly evolved according to different foods and feeding habits. Therefore, studying the structure of the mouthparts is the key to understanding their feeding mechanisms. Vibidia duodecimguttata is an important biological control agent for powdery fungus. In this study, the fine morphology of the mouthpart of V. duodecimguttata was studied by scanning electron microscopy. The basic components of mouthpart of V. duodecimguttata are similar to those of other ladybeetles, while the specific morphology of each part is different. In total, six kinds of sensilla were identified on mouthpart, and twelve types of sensilla were divided according to their morphology, length and distribution. In addition, two kinds of glandular structures were also found, perforated plates and cuticular pores. Finally, the morphological differences between mycetophagous and other feeding habits ladybeetles were compared, and the function of each kind of sensilla were discussed, which may lay a solid foundation for further understanding of the feeding mechanism of ladybirds.