Abstract: he ultra-morphology and chemical composition of the waxes secreted by the scale insect, Eulecanium gigantea, in different development stages were studied with scanning electron microscope and infrared spectra techniques. The results showed that waxes secreted by the young nymph were wet. They first coagulated into many granular structures in different sizes, then linked into greater pieces and plates, finally heaped up into a turtle-shell-form wax covering the dorsal surface of the scale insect. Each plate of the wax covering was corresponding in position with the projecting integument area, on which the wax pores are densely distributed. In the young stage, the wax coverings possessed the equal texture for both sexes. However, the adult female secreted many long, coil and hollow wax threads. The infrared absorption spectra of waxes indicated that for the female adult stage, the wax secretions were of the same chemical functional groups and compositions, no matter whether they were secreted from dorsal or ventral surface. In spite of the basic similarity in chemical compositions of the waxes secreted by the female and the male, some significant differences were found. In the male's infrared spectra there were two peaks around the site of vibration frequency 1 736.3 cm^-1, but only one peak at the same site for the female's. Furthermore, in the male's spectra, there were 3 peaks in the vibration frequencies 1 242.0 cm^-1～1 106.6 cm^-1 for the functional group C—O absorbing vibration. However, in the same frequencies, there was a series of sawtoothform peaks showing long carbon chain —C—C—C— absorbing vibration in the female's spectra. Based on the infrared spectra, it was suggested that the scale insect's waxes be composed most by longchain hydrocarbons, fatty alcohols, fatty acids and some compounds with aromatic rings.

Key words: Eulecanium gigantea, waxes, ultramorphology, chemical composition, infrared spectra