This is the report of my study on the preoviposition period, egg maturation and resorption of the ovarian eggs of Tetrastichus sugitamabae Yasumatsu et Yoshii, an important larval parasite of Contarinia inouyei Mani. This work was carried out in the laboratory from June of 1964 to May of 1965. The material (twigs of Cryptomeria tree) haboring galls of Contarinia inouyei was collected at Iino in Miyazaki Prefecture and kept in the rearing boxes to get the larval parasites in question. The emerged females of the parasite were fed with honey and water in separate vials with males or without males. The following results were obtained. The female of this parasite is synovigenic and the egg is anhydropic. The preoviposition period lasts approximateley 4 days after emergence in all generations. In the first generation, the oviposition period is about 11 days in the mated female and 6 days in the virgin female. In the second generation, this period is 16 days in the mated female and 13 days in the virgin female, while 26 days in the virgin female of the overwintering generation. The mean number of the mature and half-mature eggs in the ovary of the mated female is more than that found in the virgin female in all generations. In the oviposition period, the mean number of the mature eggs is not constant. It seems to be due to a difference of the rate of egg maturation and resorption. In mated fem a les rapid resorption occurs from about 16 days after emergence in the first generation and 21 days in the second generation. In virgin females it occurs from about 11 days in the first generation, 18 days in the second generation and 31 days after emergence in the overwintering generation. The fact that the species has a longer oviposition period has proved the effectiveness of this parasite in controlling the larvae of Contarinia inouyei.