Based on the experimental data from Anqing City,Anhui Province in 1996 and Jiangpu County,Jiangsu Province in 1997,the natural control functions of spider community to rice planthopper were studied by using two indexes,the capacity of environment( K )and reproduction rate The enemy function index( EF ) its formula were put forward firstly The results showed that there was significant negative correlation between the EF value and rice injured rate by planthopper The K value and reproduction r...