Abstract: To locate the organs on which the quinolizidine alkaloid sensilla of Plagiodera versicolora are distributed, bioassay methods were set up. Cutting off the organs physically or denaturing of the sensilla chemically on the organs, then bioassaying oviposition selection on alkaloid treated and untreated leaves in treated adults to determine the organs on which the alkaloid sensilla were located. The results of the bioassay by chemically denaturing the sensilla of the possible organs showed that the sensilla for the alkaloid in P. versicolora were mainly located on maxillary palpi, labial palpi, and tarsi of the fore legs. However, denatu ring of the sensilla on the antenna bad no effects on the oviposition selection of the adults. Based on the results of the bioassay,the sensilla on mandibles, maxillae and tarsi of the legs were observed by Scanning Electron Microscope (SEM). The results showed that there was only single type of sensilla on the tips of maxillary palpi, labial palpi. Therefore, the alkaloid sensilla of P. versicolora were likely the styloconic sensillum on the tips of maxillary palpi, labial palpi and the trichoid sensilla on the tarsi of the fore legs.