Abstract: The endogenous enzymes of protective system including superoxide dismutase(SOD), peroxidase (POD) and catalase (CAT) were found to exist in the larvae of Pieris rapae. The level of SOD activity of the larva was closely correlated with the instars. After applying deltamethrin to the larvae, the levels of SOD, CAT and PODactivity were found to be higher than that of the control within one hour. When deltamethrin was applied to the slug caterpillars Parasa consocia and Thosea pastornata, the SOD and CAT activities were enhanced gradually with the degree of poisoning, but declined rapidly near death. However, the SOD and CAT activities in the slug caterpillars survived from the deltamethrin treatment were higher than that of the control, showing that SOD and CAT activities were correlated with tolerance to insecticide.

Key words: Pieris rapae——slug caterpillar——superoxide dismutase——cata-lase——peroxidase