The structure ki mutant chorion is described by the ultrastructural level with the scanning electron microscope. The micropyle on the anterior, posterior, leteral and dorsal side region surface patterns do not so much differ from ki mutant and normal strains. The surface structure of ventral side of ki mutant, which is the presumptive embryonic region in oocytes, were netted part corresponding to the boundary of follicle cells that is similar to lateral side structure of egg-shell. The eggshell thickness of ventral side on the ki mutant is mostly thicker. However, the structure of transverse section of normal and ki mutant egg-shell are composed of the outer, middle and inner layers. The ki not effects the formation of the lamellar layer in the egg-shell. It is observed that the characteristic structure in ki mutant egg chorion may be attributed to a areal specificity of epithelium in ventral side of egg-shell formation, and it affects the process of the accumulation of secreted chorionic material and the egg-shell architecture.