Sensilla of the Western Flower Thrips, Frankliniella occidentalis (Pergande) (Thysanoptera, Thripidae)

The sensilla of insects play important roles in odor, taste, the feeling environment, and some sensory functions, which are closely associated with insect host locating, feeding, habitat searching, courtship, mating, and oviposition. In this study, we used a scanning electron microscope to observe the external morphology of nymph and adult Frankliniella occidentalis sensilla on antennae, compound eyes, legs, mouthparts, wings and tail. The results show that three main types of sensilla are located on the antennae: sensilla trichodea, sensilla chaetica, and sensilla basiconica. Among them, sensilla trichodea are the most abundant, followed by sensilla chaetica. Sensilla basiconica on antennae are divided into seven sub-styles, including longer sensilla (L-sensilla basiconica, long sensilla basiconica), shorter sensilla (angle sensilla basiconica, bud sensilla basiconica), and thicker and bigger sensilla (stick sensilla basiconica, fork sensilla basiconica, and finger sensilla basiconica). Only two fork sensilla basiconica were found, located on the dorsal part of the first flagellum subsegment and the ventral part of the second flagellum subsegment, respectively. Seven sensillum types were found on the legs: sensilla trichodea, sensilla chaetica, sensilla basiconica, sensilla ear washing buob-shaped, mamillary sensilla, sensilla campaniform, and Böhm bristle. About 60% of them are sensilla chaetica. Only one sensillum type was found on compound eyes: sensilla chaetica. In addition, some sensillum types were also found on the mouthparts, wings and tail, respectively. In the study, we observed the type, morphology, and distribution of sensilla on antennae, legs, compound eyes, and other regions of nymph and adult F. occidentalis, forming a base for future electrophysiological and behavior experiments on F. occidentalis.