Abstract: The coefficient b in Taylor's power law has been interpreted as an index of aggregation,with characteristic value for a given species, and indepondent of sampling environment.Systematic samplings of aphids on crucifer vegetables were carried out during 1985-1992 in the suburb of Hangzhou. The results of test showed that the estimated values of Taylor's b of the two aphids,Myzus persicae and Lipaphis erysimi were significantly interspecifically different.However for a given species,the b values were not constant among sampling populations in different environment. It should be pointed out that different sampling coverage may lead to the inconstancy of b.Therefore,cautions should be given in the use of b for explaining spatial behaviors or comparing interspecific difference of aggregation.

Key words: Pinus tabulaeformis, gap size, seedling regeneration, path analysis.