Comparative morphology of sensilla on the antennae, maxillary and labial palps in different larval instars of Cryptorrhynchus lapathi (Linnaeus) (Coleoptera: Curculionidae)

Cryptorrhynchus lapathi (Linnaeus) (Coleoptera: Curculionidae) is an important cosmopolitan wood-boring insect pest. Its larval stages damage salicaceous plants and thereby cause serious economic losses to the forest industry. In this study, we used scanning electron microscopy to record the number, typology, morphology, and distribution of sensilla on the antennae, maxillary and labial palps in the third, fourth, and fifth larval instars of C. lapathi. Two types of sensilla were observed on the antennae: sensilla basiconica (S.b.1) and sensilla twig basiconica (S.tb.1-4). The maxillary palps had three types of sensilla, S.b.2, S.tb. (S.tb.4-6), and sensilla digiformia (S.d.), while two types were found on the labial palps, S.b.2 and S.tb. (S.tb.4-6). The numbers and types of antennal, maxillary and labial palp sensilla remained unchanged in different larval instars, but the length and diameter of sensilla generally increased throughout larval development. Sensilla distributions on the maxillary and labial palps were significantly different in successive instars, but there were no differences on the antennae. We discussed the functions of sensilla in wood-boring behavior. These results may provide a theoretical basis for further studies of feeding behavior and electrophysiology of C. lapathi larvae. (C) 2019 Elsevier GmbH. All rights reserved.