Abstract: Temperature is a most important factor affecting insect development and the activity of insect symbiotic microbial. In order to explore the effects of high temperature on the reproduction, developmental traits, and Wolbachia infection of the parasitic wasp, Sclerodermus sichuanensis, the parasitoids reared under three temperatures (27, 30, and 33℃) for four consecutive generations were observed for the parasitism ability and pre-oviposition period of female, progeny developmental duration, offspring number, and male proportion. Meanwhile, the Wolbachia infection of the female parasitoids was detected using the specific primers of the outer surface protein gene (wsp). The results showed that high temperature had no significant effect on the females' parasitism ability, but significantly influenced on their pro-oviposition period and progeny development. With the increase of temperature, the pre-oviposition period of females was prolonged, but the durations of immature stage were significantly shortened. The duration of egg stage was 4.33, 3.27, and 3.36 d; duration of larval stage was 6.77, 5.85, 5.07 d; duration of pupal stage was 13.85, 12.35, 10.96 d in the three temperature treatments, respectively. The durations of parasitoid immature stage at 33℃ were shortened by approximately 5 d in comparison to parasitoids rearing at 27℃. There were no significant differences in the offspring numbers at different temperatures, but the male numbers and proportions exhibited significant increase with the increasing temperatures. Male numbers and proportions of parasitoids reared at 33℃ were approximately three times larger than those at 27℃. Additionally, all the parasitoid individuals were infected by Wolbachia after four generations of breeding at 27℃; however, Wolbachia infection rate of female parasitoids decreased to 6.67% at 33℃. There is a significant negative correlation between temperature and Wolbachia infection rate. Our findings indicate that high temperature shortens the developmental durations of the parasitoids, but also results in the reproductive fitness loss attributed to the significantly increased of male proportions. Our results also confirm that the activity of Wolbachia is inhibited at high temperature, and thus accordingly increases the proportion of the male offspring. The temperature of artificial mass-rearing of the parasitoid, S. sichuanensis, should not exceed 30℃.

Key words: Sclerodermus sichuanensis, temperature, developmental duration, offspring number, Wolbachia