Field surveys were carried out at five days interval in the single rice-growing season in Hangzhou in 1999. The rice crop were transplanted on June 23 and harvested on October 3. Using a plate inserted at the base of the plants, the numbers of Nilaparvata lugens and Pardosa pseudoannulata per hill were counted by eye. Counts were taken for 20 samples, 2 hills for each sample. Field investigation showed that the maximal densities of N. lugens and P. pseudoannulata were 126 /hill and 1.83 /hill, respectively....