Abstract: In a systematic study on the Lishui Forestry Farm, Jiangsu province from 1983 to 1986, it was found that feces amount of pine caterpillar (Dendrolimus punctalus Walker) varied regularly with different ages of different generations and that feces amount of pine caterpillar could easiely and reliably be used to accurately determine insect density in high and big trees which are difficult to investigate.