We investigated the gross and ultrastructure morphology of the mandibles, labial palpus and mandibular palpus of adult male and female Glenea cantor beetles using scanning electron microscopy. There were significant differences between males and females in the gross and ultrastructure morphology of these parts. Observation of the gross morphology of the mandible, labial palpus and mandibular palpus revealed that their lengths were significantly greater in females, which is mainly related to the oviposition mechanism. In terms of the ultrastructural morphology of the mandibles, labial palpus and mandibular palpus, seven types of sensilla were found on these parts: sensilla twig basiconica (STB I, II, III, and IV), sensilla chaetica (SCh IV and V), Böhm’s bristles (Bb), sensilla placodea (SP), sensilla trichodea (ST II), sensilla plate (SP), sensilla coeloconica (SC) and sensilla campaniformia (SCa). Females have significantly more ST I and SCh III on their mandibles than males. The mechanical sensors SCh and Bb, olfactory sensor ST II, taste sensor STB IV, and carbon dioxide sensor and temperature and humidity sensors SC, SP and SCa were significantly more developed on female than male labial and maxillary palps, which also further explained the important role of the oral appendages in oviposition behavior. These results will help us further understand the host selection and oviposition behavior of adult G. cantor and promote the information-based design of pest control methods.