Morphological comparison of the sensilla on the maxillary and labial palps between male and female adults of Moechotypa diphysis (Coleoptera: Cerambycidae).

Moechotypa diphysis (Pascoe) is one of the most important pests in agriculture and forestry. However, there are few studies focusing on the external morphology of M. diphysis adults. In this study, the mouthparts of M. diphysis adults were observed by the scanning electron microscope to compare the quantity and distribution of the sensilla on the maxillary and labial palps. The results showed that there are four segments on the maxillary palps and three segments on the labial palps. The length of each segment of the maxillary and labial palps is larger in the female than that in the male. Six types of sensilla are found on the maxillary and labial palps of M. diphysis adults: sensilla basiconca (SB1, 2, 3, and 4), sensilla trichodea (ST1, 2 and 3), sensilla chaetica (SC), sensilla placodea (SP), hair plate (HP) and sensilla coeloconica (SCo). There is no significant difference in the number of most types of sensilla between females and males in the same position. However, the number of ST1 on the maxillary and labial palps is significantly higher in the female than in the male. In addition, the number of most types of sensilla (SB2, ST1, SC, SP, HP, and SCo) on the maxillary palps is significantly higher than on the labial palps both for females and males. Maxillary palps may play a more important role in the activities of M. diphysis adults than the labial palps. Based on this study, we discussed the functions of the sensilla on the maxillary and labial palps of M. diphysis adults to provide the theoretical basis and statistical data for further research on the behavior and the electrophysiology of this devastating forest pest.