Abstract: 【Aim】 Based on the complex relationship of competition and parasitism between two parasitic natural enemies, Beauveria bassiana and Sclerodermus guani in natural microhabitats, the adaptive reproductive strategies of parasitoids under the stress of B. bassiana were investigated, and the lethal and parasitic effects of the parental parasitoid carrying B. bassiana on itself and its offspring were comprehensively evaluated. 【Methods】 After the female adults of the parent (F₄₈ generation) of S. guani were treated with the spore suspension of B. bassiana at different concentrations (1×10⁴, 1×10⁵ and 1×10⁶ conidia/mL) by the immersion method, and put into the test tubes containing the host Monochamus alternatus larvae, the mortality, cumulative mortality and corrected mortality, pre-oviposition period, oviposition period, total fecundity (total number of eggs laid) and number of eggs laid per female of the adults of the parent (F₄₈ generation), and the mean developmental duration, survival rates, body weight per female and proportion of males of the corresponding offspring (F₄₉ and F₅₀ generations) were tested, and the dose and time effects of B. bassiana on the female adults of F₄₈ and F₄₉ generations during the lethal process were also determined by using the time-dose-mortality model (TDM). 【Results】 The pathogen load of S. guani female adults of the parent (F₄₈ generation) increased with increasing concentration of B. bassiana spore suspension, with the average initial pathogen load of about 0.91×10⁴, 1.73×10⁴ and 1.95×10⁴ conidia/female, respectively, under the concentrations of 1×10⁴, 1×10⁵ and 1×10⁶ conidia/mL. Subsequently, B. bassiana was passed from the female adults of the parent (F₄₈ generation) to the offspring (F₄₉ generation) of S. guani, with an average initial pathogen load of 0.78×10⁴, 1.40×10⁴ and 1.51×10⁴ conidia/female, respectively, under the concentrations of 1×10⁴, 1×10⁵ and 1×10⁶ conidia/mL. This phenomenon of carrying B. bassiana by S. guani (F₄₈ generation) not only affected the longevity and reproduction of the female adults of F₄₈ and F₄₉ generations of S. guani, but also affected the fitness of their corresponding offspring (F₄₉ and F₅₀ generations). Compared with the control (non-inoculation with B. bassiana), the stress of different concentrations of B. bassiana spore suspension resulted in a series of significant changes in the performance of the female adults of the parent (F₄₈ generation) and the corresponding offspring (F₄₉ generation), including the mean pre-oviposition period was shortened (F₄₈: shortened by 1.03, 1.43 and 2.03 d, respectively; F₄₉: shorted by 0.30, 0.80 and 1.00 d, respectively), the mean oviposition period was extended (F₄₈: extended by 0.30, 1.00 and 1.30 d, respectively; F₄₉: extended by 0.43, 0.73 and 1.43 d, respectively), the total number of eggs laid increased (F₄₈: increased by 4.80, 17.16 and 10.33 grains, respectively; F₄₉: increased by 11.57, 25.04 and 9.14 grains), and the number of eggs laid per female decreased (F₄₈: decreased by 4.07, 7.06 and 15.98 grains, respectively; F₄₉: decreased by 5.30, 9.37 and 20.47 grains, respectively). Similarly, the fitness of the corresponding offspring (F₄₉ and F₅₀ generations) of S. guani showed the same change trend. Overall, due to the transmission of B. bassiana at different concentrations (1×10⁴, 1×10⁵ and 1×10⁶ conidia/mL) carried by the female adults of the parent (F₄₈ generation) of S. guani, the developmental process of its offspring (F₄₉ and F₅₀ generations) was obviously accelerated. After B. bassiana carried by the parent female adults of S. guani (F₄₈ generation) was passed to the offspring, the generation time of the F₅₀ generation was shortened by 3.00, 3.00 and 4.00 d, respectively, the survival rate and emergence rate of the F₅₀ generation were decreased by 16.21% and 19.40%, respectively, the body weight per female actually increased by 0.09 and 0.94 mg, respectively, and the proportion of male offspring significantly decreased by 1.95% and 0.22%, respectively, as compared to those in the control. The TDM model showed that after inoculation with a high concentration (1×10⁶ conidia/mL) of B. bassiana spore suspension, the female adults of the parent (F₄₈ generation) of S. guani reached 50.83% mortality at 20 d after inoculation, while their corresponding offspring (F₄₉ generation) reached 50.00% mortality at 18 d after emergence. The LT₅₀ value of 1×10⁶ conidia/mL of B. bassiana spore suspension against the parent female adults of S. guani was 22.72 d, and that against the female adults of the F₄₉ generation was 24.352 d. Simultaneously, under other concentrations (1×10⁴ and 1×10⁵ conidia/mL) of B. bassiana spore suspension, the mortality of the female adults of F₄₈ and F₄₉ generations was less than 40.00%. 【Conclusion】 In response to B. bassiana stress, the parent female adults of S. guani not only reduce their fertility, but also indirectly affect the survival and development of their offspring. The concentrations of B. bassiana carried by the parent female adults of S. guani have a direct effect on the cumulative mortality of themselves and the female adults of the offspring, which increase with the increase in the concentration of B. bassiana spore suspension and test time. The dose and time effects of B. bassiana on the lethal process of S. guani show a significant interactive relationship.

Key words: Sclerodermus guani, Beauveria bassiana, maternal care, intergenerational effect, TDM model