The study showed that the searching activity of P. japonica on cotton aphid Aphis gossypii decreased gradually with decreasing aphid density. When enough A. gossypii existed, P. japonica had a preferential searching and preying activity on the top of cotton plant. There was no significant difference in the preying activity of P. japonica at different positions of cotton plant, while the searching activity of the ladybird beetle was significantly lower on cotton M9101 than on cotton Zhongmian 13. The preying behavior of P. japonica was sign...