Abstract: The ultra-morphology and chemical composition of the waxes secreted by the scale insect, Didesmococcus koreanus Borchs, was studied with scanning electron microscope and infrared spectra techniques. It was found that the waxes secreted by the young nymphs are long threads in its shape. Quite the contrary, the waxes changed their shape into granular, mass and piece on the dorsal surface of the old nymphs and adult females. By comparing the characteristics of the infrared absorption spectra of the waxes, the conclusion is that the main kind of chemical function groups and compositions are basic the same or similar in the two waxes secreted respectively by the young scale insect and the old one. A mid-strong absorption peak at 1 240.7 cm^-1 indicated the male scale insect's waxy cover having a different function group. Therefore, its composition is different to the female one's and the young nymph's. Based on the infrared spectra, it is suggested that the scale insect's waxy compounds are composed majorly by longchain fatty alcohol and fatty acids and some compounds with aromatic ring.

Key words: Didesmococcus koreanus, waxes, ultramorphology, chemical composition, infrared spectra