CYTOCHEMICAL DEMONSTRATION OF CHITIN INCORPORATION IN THE CUTICLE OF TRIALEURODES-VAPORARIORUM (WESTWOOD) (HOMOPTERA, ALEYRODIDAE) AFTER BUPROFEZIN TREATMENT

Buprofezin is an insect growth regulator acting specifically against sucking insects. Nymphs of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Homoptera : Aleyrodidae) were treated with different concentrations of this compound and the deposition of the chitin in the integument examined. The lectin, wheat germ agglutinin (WGA), which binds specifically to N-acetylglucosamine-containing polymers, conjugated with colloidal gold, was used as an electron-dense marker for localizing chitin on ultrathin sections. In untreated insects, the epicuticle and epidermis cells were devoid of label, while the procuticle was heavily labelled. In buprofezin-treated nymphs, only the pre-apolysial cuticle remained heavily labelled, independent of the concentration used. The post-apolysial cuticle, however, was hardly labelled, the intensity of labelling depending on the applied concentration, and its thickness severely reduced. These results suggest that buprofezin affects only post-apolysial cuticle in a concentration-dependent way.