Abstract: Nylon net method was used to study the interactive effect between Nilaparvata lugens and Sogatella furcifera nymphae. The result shows that an interactive process was existed in different degrees between these two kinds of nympha. The expression of biological characteristics of the two planthoppers, such as emergence, sex, wing form, female's body length and weight, was affected in some degrees by the existence of each other. With an increasing proportion of N. lugens, the expression mentioned above of S. furcifera became more obvious, and vice versa, that of N. lugens was little. The effect of interspecific density was far greater than that of intraspecies, indicating that there existed a difference to the interspecific reaction between the biological characteristics of the two planthoppers.

Key words: Nilaparvata lugens, Sogatella furcifera, Nympha, Interactive effect