Mechanisms Underlying the Differential Susceptibility of the Larvae and Adults of Trogoderma granarium Everts to Parathion and Paraoxon

The larvae of Khapra beetle, Trogodema aranarium Everts were more tolerant to papathion and papaoxon than the adults. The mechanisms of this differential toxicity were investigated. The penetration of C—ring labelled parathion and paraoxon was higher in the adults as compared to the larvae. Both larvae and adults metabolised the insecticides rapidly via a number of metabolic pathways. Following the application of C-Parathion, the level of the metabolite paraoxon formed was 5 to 7 time intervals. Further, the slight increased detoxication of paraoxon by cleavage of the P (O)-O aryl bond in the larvae was observed. The larvae excreted about 2 to 3 times more of water-soluble metabolites of parathion and paraoxon compared to adults. Tolerance in the larvae was also found to be associated with a 8—fold decrease in sensitivity of acetylcholinesterase to paraxon inhibition.