Induction of microsomal oxidase in F1 hybrids of a high and a low oxidase housefly strain.

Microsomal oxidase activity is increased up to sixfold in dieldrin-resistant houseflies exposed to sublethal doses of dieldrin. The net increase in enzyme activity is greater in a strain initially high in oxidase activity than in a strain low in this respect, and this tendency is carried into the F(1) hybrids of the strains.