Abstract: The article compared the number of offspring, developmental biology, and sex ratio of Sclerodermus alternatusi Yang (Hymenoptera: Bethylidae) in order to investigate the effect of parasitoid age on the length of the immature stage and brood size of offspring. One parasitoid per host was inoculated on Thyestilla gebleri larvae at intervals of 15 days under normal temperature conditions after the female emerged. The findings indicated that there was no discernible change between the parasitism and successful parasitism rates as parasitoid age increased. At different parasitoid ages, there were significant differences in the pre-oviposition duration of the female, the larval stage, the pupal stage, and the offspring’s developmental duration; however, there was no significant difference in the egg stage durations. The sizes of the female offspring and the total number of offspring varied significantly depending on the parasitoid's age. For example, when the mother female was 15 days old, 43.21 females and 47.21 offspring emerged from one host; when the mother female was 1 day, 30 days, and 45 days old, the number of females and offspring decreased slightly; and when the mother female was 60 days old, 26.12 females and 28.88 offspring obtained from one host. The number of male progeny that emerged from a single host was approximately 2—4; there was no discernible variation in the parasitoid ages, and the number of female offspring was substantially lower. At five mother female ages, the male offspring ratios were less than 10%, and at varied parasitoid ages, the winged female offspring significantly declined and were all less than 20%. When the mother female was less than 45 days old, the parasitoid would maintain parasitism effectively at room temperature and lay an adequate number of eggs. New sources for raising and managing S. alternatusi to suppress longhorn beetles are supplied by this work.

Key words: Sclerodermus alternatusi, age, length of immature stage, brood size