Abstract: The ultra-morphology and chemical composition of waxes secreted by the scale insect Dicyphococcus bigibbus Borchsenius (Homoptera: Coccidae) was studied with the techniques of scanning electron microscope (SEM), infrared absorption spectra (IS) and gas hromatography/mass spectrometry (GC/MS). The results indicate that the wax secretions are wet at first from the glands in both nymph and adult stages. Then they coagulated into dry and glassy wax test over the body surface. The wax test with a hard and fragile quality consists of many vertical pillar-like ridges with horizontal layer upon layer. The wax tests of the young nymphs and male scale insects are small, ship-shaped, central dorsal region elevated highly and with some wax fringes around the body margin. Female wax test is larger, v-shaped at its top. The infrared spectra of the wax secretion show the characteristics for species in sharp and dense peaks. The main chemical function groups and compositions of the wax secretion are conjectured based on its infrared absorption spectra, and verified with the results of GC/MS. Through esterification and unesterification, It is found that the waxes are composed of a series of greater molecular compounds, i.e., long chain saturated and unsaturated hydrocarbons, fatty acids and esters. Their carbon atom numbers mostly are even number and range from C₁₄ to C₄₀. The proportion of ester compound is greater especially than those with carbon a toms C₃₀ to C₄₀. The wax characteristics of this scale insect were compared with that of other species in the same family, Coccidae, e.g., Eulecanium gigantea, Didesmococcus koreanus, Eriopeltis festucae and Ericerus pela. The significances of the wax secretion for the classification, systematics and control of scale insects are discussed.

Key words: Coccidae, Dicyphococcus bigibbus, waxes, ultra-morphology, chemical composition