Based on the mechanism of differentiation of Dendrolimus punctatus in the area with the latitude of 30° N,the differentiation rates of the second and third generation can be determined by evaluating the hatching rate of the second generation larvae,so as to forecast the dynamics trend of local populations. The practical forecast and verification conducted in Gaoan,Wannian,Yujiang and Linchuan counties of Jiangxi Province in 1993 proved that it is feasible to forecast the differentiatin of the second and third generation by critical differentiation date.
