Euploea core is a long lived butterfly which lays a few relatively large eggs each day. In such a species it is unlikely that reserves of carbohydrate and amino acid accumulated during the larval instars would be sufficient to last its entire adult life. Female E. core were kept in a large flight cage and assigned to one of four treatments. Each treatment comprised a different concentration of sugar and amino acid in the adult diet of the butterflies. Individuals with 25% sugar in their diet lived for longer and attained higher fecundities than those with 1% sugar in their diet. Butterflies on the 1% sugar diet removed greater volumes of food solution than those on the 25% sugar diet. The availability of amino acids in the adult diet had no marked effect on longevity and, if anything, had a negative effect on fecundity. The composition of the adult diet had no discernable effect on egg weight in this species. Sugar is shown to be an important component of the adult diet of E. core but their requirement for amino acids in their adult diet remains unresolved. Finally, using the known volume of food solution removed each day, estimates were made of the minimum amount of energy required by this species each day and the amount of energy required to produce an egg.