Abstract: 【Aim】 The horned gall aphid, Schlechtendalia chinensis, is the major productive species of Chinese gallnuts. S. chinensis exhibits complex life cycles, including alteration of sexual and asexual reproduction via host switch between Chinese sumac (Rhus chinensis) and mosses. There are six body forms, i.e., fundatrix, fundatrigeniae, fundatrispuriae, apterae, sexuaparae, and sexual forms, alternating inside and outside a gall to finish its whole life cycle. 【Methods】 Specimens of various body forms of S. chinensis were obtained from S. chinensis reared in the laboratory based on the original population of S. chinensis collected from the fields in Yanjin, Yunnan, southwestern China. The distribution, morphology, and structure of wax glands in S. chinensis were investigated using light microscope, electron microscope, and technique of ultrathin section. 【Results】 All body forms of S. chinensis except the 1st instar fundatrix possess wax glands on the dorsum, including 2 columns and 2 rows on the head, 4 columns and 1 row on the thorax, 6 columns and 8 rows on the abdomen, with a total of 56 wax glands. No wax glands appear on the dorsum of the 1st instar fundatrix (living outside a gall), but there are 2 columns and 8 rows of wax glands (in total 16 wax glands) on the dorsum of the 2nd instar fundatrix (living inside a gall). Each wax gland is composed of 2-22 polygonal depressions, and the number and morphology of depressions are obviously different among various body forms. The wax glands of fundatrigeniae, sexuaparae, and fundatrispuriae are the most complicated, and followed by apterae. Furthermore, the structure of wax glands in different parts of the sexual forms is significantly different: the wax gland structure of the dorsal plate and dorsolateral plate near the midline is simple, while that near the lateral line is complex. The wax gland structure of the 2nd instar fundatrix is simple as well. Corresponding to the distribution of wax glands, waxes appear on the body surface of all body forms except the 1st instar fundatrix. Fundatrigeniae, sexuaparae, and fundatrispuriae secrete a large amount of wax, followed by apterae. There is a small amount of wax on the body surface of the sexual forms and the 2nd instar fundatrix, whereas no wax exists on the body surface of the 1st instar fundatrix. 【Conclusion】 The number, arrangement, and development of wax glands on various body forms of S. chinensis are different. These differences are closely related to the microenvironments in which they live and the biological characteristics of each stage, being probably the long-term adaptation of the horned gall aphid to environmental conditions.

Key words: Schlechtendalia chinensis, wax gland, ultrastructure, body form, ecological adaptation