Abstract: Spatial distribution patterns for egg-masses,larvae and pupae of the pine caterpillar were measured by means of several indexes of aggregation.Frequency distribution of egg-masses fits to poisson distribution,and that of the larve and pupae obeys aggregation distribution,but the aggregation indexes are the highest in small larve and lowest in pupae. Lwao's method of regression of mean crowding(x) on mean density(x)is a good method for detecting the aggregation patterns.In the pine caterpillar,larve and pupae,all x-x relation in a series of distribution is fitted to a single linear regression for a>0,β>1.Lwao's equations for data transformation were applied and tested for its fitness,the transformed data all obey normal distribution and the tests of homogeneity variance indicate that the results of transformation are well fitted.From this method the optimal sampling size is determined,the sequential analysis is also applied.