Abstract:Thermal avoidance and distribution of Rhopalosiphum padi in temperature gradients were investigated with self-made temperature gradient apparatus. Thermal avoidance rate of the aphids was evidently increased by increasing the temperature difference between the two ends of temperature gradient fields. Thermal avoidance rate of the aphids was 52.5%, 72.5%, 92.1% and 100% when the temperature gradients were settled as 27.0-22.7℃, 32.0-23.8℃, 37.0-25.3℃ and 42.0-27.7℃, respectively. Acclimating adults at 15℃ for 1.5h had a higher thermal avoidance rate (77.5%) than those at 35℃ for the same time (64.2%), suggesting that the adults have the ability to adapt to high temperature. Thermal avoidance rate of different developmental stages of tested aphids showed no significant difference. In the leaf temperature gradient (26-43℃), 50% of tested R. padi distributed in the area of <27.7℃, and 99% of the aphids distributed <32.0℃. 99% of 1st instar nymphs distributed in the area of <32.7℃, while 99% of 3rd instar nymphs distributed in <30.0℃.