The demethylation of p nitroanisole in various tissues of cotton bollworm, Helicoverpa armigera , was examined. The highest activity of demethylase was found in midgut and fat body. Relatively low activities were expressed in foregut, Malpigian tubules and hind gut. No detectable demethylation existed in testis and integument tissues. Low aldrin epoxylation was detected in integument relative to midgut, and the potential endogenous inhibitor was proved not to be the cause for low p nitroanisole...