THE CONVERSION OF DDT TO DDE BY SOME ANOPHELINES.

The metabolism of DDT has been followed in pure lines of laboratory-reared resistant and susceptible anophelines using gas-liquid chromatography. Relatively large amounts of DDE were formed in vivo by susceptible strains of Anopheles stephensi, A. quadrimaculatus and A. gambiae, and by resistant strains of A. stephensi and A. quadrimaculatus. Resistant and susceptible A. albimanus showed no difference in the rate of DDE production. Volatile metabolites of DDT other than DDE were not observed in most of the strains chromatographed. A procedure for the measurement of DDT-dehydrochlorinase in small numbers of mosquitos was devised based on conditions developed for the glutathione-dependent DDT-dehydrochlorinase present in resistant houseflies. This method has shown the enzyme to occur in highest titre in DDT-susceptible A. albimanus and A. stephensi, indicating little or no correlation with resistance to DDT. Major differences in dehydro-chlorination rates and in patterns of resistance between anopheline species have been observed. In A. stephensi, these differences extend to the level of strains.