The essential role of folic acid and the effect of antimetabolites on growth and metamorphosis of housefly larvae Musca domestica L.

Abstract Housefly larvae reared on a defined diet under aseptic conditions show complete dependence on dietary folic acid (PGA) for normal growth and metamorphosis. Larvae cannot synthesize PGA from available precursors; neither can they synthesize DNA and RNA from purine and pyrimidine bases in the absence of folic acid. Aminopterin and pyrimethamine reversibly inhibit the enzyme folic acid reductase which catalyses the reduction of folic acid to tetrahydrofolic acid. As a consequence, larval growth and metamorphosis are impaired. 5-Fluorouracil, azaserine, 3-aminotriazole and fluoroacetamide are potent inhibitors of larval development but their action is not reversed by folic acid.