Abstract: Dilute solutions of atrazine and dichlorvos were used to treat the larvae of cotton boll worm Heliothis armigera and housefly Musca domestica vicina by topic application or mixing them with the diets for rearing the larvae. The activities of carboxylesterase (CarE) and glutatione-S-transferase (CST), using the supernatant protions of the homogenates of the larvae,were determined according to the methods of Asperen (1962) and Habig ct al (1981) respec tively. The results showed that atrazine induced Gate and GST activities significantly in the cotton bollworm to about 146% and 280% respectively. The peak of Care activity induced byatrazine appeared earlier than that of GST. Both the time and magnitude of Care or GST activity varied with the amount of atrzine used in the topic application. In the larvae of house fly, dichlorvos was very poor inducer of Care or GST activity and atrazine could not increase GST activity.

Key words: Heliothis armigera——Murca domestica vicina——carboxylesterase—— glutathione-S-transferase——enzymic induction