Abstract Modifications are described in the formulation of an artificial diet for rearing Myzus persicae. Using this aphid species and the dietary improvements, we determined the relative growth of larvae, derived from ascorbic acid-deprived apterous mothers, on diets containing ascorbic acid or related compounds at various concentrations. l-Dehydroascorbic acid (the oxidized form of l-ascorbic acid) is utilizable, but only about 50 per cent as efficiently as equivalent amounts of l-ascorbic acid. d-Araboascorbic acid (an epimer of l-ascorbic acid about C 5) is almost equivalent to l-ascorbic acid. d-Glucurono-γ-lactone and l-gulono-γ-lactone (intermediates in the biosynthesis of ascorbic acid in some mammals) are not utilized to any extent, nor was reduced glutathione (an unrelated reducing substance). The results are discussed in relation to the enzyme specificity and biosynthetic capabilities of other insects and animals.