δ15N analyses of butterfly wings and bodies suggest minimal nitrogen absorption in carrion and dung puddling butterflies (Lepidoptera: Nymphalidae)

Abstract

Nitrogenous compounds in the adult diet can play an important role in the nutritional ecology and life history evolution of butterflies. We compared the concentration of δ 15N in fruit- feeding butterflies that feed on faeces and carrion (puddling) versus those that do not feed on these substrates, and used the difference between δ 15 N in bodies versus wings as a measure of the amount of nitrogen derived from animals. Differences between the sexes and between the feeding guilds were small, suggesting that minimal amounts of nitrogen were absorbed from these resources. Males, the sex that does most of the puddling, had higher δ 15 N, but this occurred in both carrion feeders and non carrion feeders. This probably reflects differences in metabolic activity of caterpillars. It appears that caterpillar metabolism and metamorphosis results in significant secondary? δ 15 N enrichment and differences among the sexes, and, together with host-plant range and quality, in within species variation in δ 15 N values.