Abstract: 【Aim】 As the main factors, the amplitude of temperature fluctuation and the change of population density affect life history traits and population dynamics of insects, and have received widespread attention. Previous studies have shown that there is a complex and significant interaction between temperature and population density, but most studies focus on constant temperature, which cannot reflect the effects of actual temperature changes in nature on insect populations. Therefore, we focused on Rhopalosiphum padi as one of major wheat pests worldwide in this study and explored the effects of temperature amplitudes and population density on the life history traits and population parameters of R. padi through the indoor simulation of field temperature fluctuations and population density. 【Methods】R. padi nymphs newly born within 4 h were treated under the conditions of different temperature amplitudes［(22±0), (22±6) and (22±12) ℃］ and population densities (1, 2, 4 and 8 individuals/tube), the development, survival, longevity and fecundity were observed daily, and the population parameters such as intrinsic rate of increase, net reproductive rate and generation time were calculated. 【Results】 At the low population density (1 individual/tube), compared with the constant temperature ［(22±0) ℃］, high temperature amplitude (22±12) ℃ prolonged the nymphal duration by 1.24 d, reduced the adult fecundity (total number of offspring produced per adult) by 19.1 individuals/adult, and decreased the intrinsic rate of increase and net reproductive rate by 0.10 d-1and 18.7, respectively, and prolonged the generation time by 1.86 d. Under the constant temperature ［(22±0) ℃］, compared with the low population density (1 individual/tube), the high population density (8 individuals/tube) reduced the adult fecundity by 24.2 individuals/adult, and the intrinsic rate of increase, net reproductive rate and generation time by 35.3 d-1, 0.05 and 0.22 d, respectively. As population density increased, the high temperature amplitude ［(22±12) ℃］ exerted a stronger inhibition effect on the nymphal development, intensively shortened the adult longevity, and intensively reduced the intrinsic rate of increase and net reproductive rate. However, high population density not only reversed some of the adverse effects of high temperature amplitude on the fecundity but also enhanced the nymphal survial. 【Conclusion】 The results of this study show the complex effects of temperature amplitude and population density on the life history traits and population dynamics of R. padi, suggesting that previous insect survival models based on constant temperature cannot accurately describe the real status of insects under temperature variations in nature. The results will improve the accuracy of predicting and forecasting the population dynamics of field pests and formulating control strategies under climate change.

Key words: Rhopalosiphum padi, climate change, temperature amplitude, population density, life history traits, population parameters