Abstract
The distribution patterns of the immature stages of the diamondback moth, Plutella xylostella, on cabbages were contagious. IWAO's (1968) m-m regreesion method showed that the basic component of the population was an aggregation of eggs for the egg stage but a single individual for the larval and the pupal stages. The significant change of α between the egg and the larval stage suggested that action of mortality factors, viz, rainfall and natural enemies, and dispersal of newly-hatched larvae might be responsible for the change. On the other hand, the similar values of α and β in larval and pupal stages suggested the absence of density-dependent dispersal or action of effective natural enemies. The application of Bacillus thuringiensis did not cause any change in the distribution pattern among the treated plots. The distribution pattern of the parasitoid, Apanteles plutellae was contagious.
