Abstract: 【Aim】The purpose of this study is to investigate the cross-generational effects of different concentrations of thiamethoxam on Riptortus pedestris populations. 【Methods】The 3rd instar nymphs of R. pedestris were fed with the soybean seeds treated with different concentrations of thiamethoxam ［LC₁₀(5.2 mg/L), LC₂₀(11.2 mg/L), LC₃₀(19.6 mg/L), LC₄₀(31.6 mg/L) and LC₅₀(49.4 mg/L)］ by liquid-dipping method for 24 h. The surviving nymphs were reared until the adults emerged and continued to breed to establish the F1 populations. The growth, development and reproduction of the F1 population were systematically recorded. And the biological parameters of the F1 population were analyzed using the age-stage two-sex life table. 【Results】After the 3rd instar nymphs of R. pedestris were fed with the soybean seeds exposed to different concentrations of thiamethoxam, the developmental duration and pre-oviposition period of the F1 population of R. pedestris were prolonged. The egg duration and nymphal duration in the treatment with LC₅₀ of thiamethoxam were the longest, being prolonged by 1.01 and 8.39 d, respectively, and the pre-oviposition period in the treatment with LC₂₀ of thiamethoxam was the longest, being prolonged by 3.54 d, as compared to those in the control (clear water). Thiamethoxam treatment shortened the longevity of adult females and males to some degree, which was reduced by 6.89 and 8.94 d, respectively, in the treatment with LC₅₀ of thiamethoxam, as compared to that in the control. Compared to the control, thiamethoxam treatment resulted in the decrease in the age-stage specific survival rate, number of eggs laid per female, intrinsic rate of increase r_m, finite rate of increase λ, net reproductive rate R₀ and population trend index I of the F1 population of R. pedestris with increasing thiamethoxam concentration, while caused the prolonged mean generation time T. Compared to the control, treatment with LC₄₀ of thiamethoxam caused the maximum reduction in the number of eggs laid per female, which were decreased by 30.37%, and treatment with LC₅₀ of thiamethoxam resulted in the maximum reduction in the intrinsic rate of increase r_m， finite rate of increase λ, net reproductive rate R₀ and population trend index I, which were decreased by 150.40%, 1.88%， 55.92% and 65.07%, respectively, and caused the longest mean generation time T, which was prolonged by 8.4679 d. 【Conclusion】The growth, development and reproduction of the F1 population of R. pedestris are still inhibited by thiamethoxam treatment to the nymphs, and the inhibitory effects increase with increasing thiamethoxam concentration. The control efficacy of thiamethoxam against R. pedestris shows cross-generational effects.

Key words: Riptortus pedestris, thiamethoxam, sublethal concentration, growth and development, population parameters