Allocation of larval and adult resources to reproduction in a fruit-feeding butterfly

1. The source of nutritional resources allocated to reproduction strongly influences reproductive and foraging strategies. While we are beginning to understand the role of adult and larval resources for nectivorous Lepidoptera, essentially nothing is known for the large number of species that feed on fruit as adults. 2. We used stable isotopes to examine allocation of larvaland adult-derived resources to egg production in a tropical frugivorous butterfly, Bicyclus anynana (Butler, 1879), under both ad libitum and semistarvation conditions. The butterfly’s larval and adult host plants differ from each other in both carbon and nitrogen isotopic ratios. 3. Adult fruit feeding is required for the onset of oviposition. 4. At peak, adult fruit feeding contributed 55% of the carbon found in eggs under both feeding conditions. This is similar to values for several nectivorous Lepidoptera with similar ovarian dynamics and egg C/N. 5. Egg N declined rapidly during the first week of oviposition, suggesting that the adult diet was not contributing nitrogen to egg production. Values rose during the following 2 weeks, consistent either with adult contribution or with isotopic fractionation. 6. Our results are consistent with the hypothesis that fruit serves as a carbon source for egg production in a similar manner as nectar. However, more work is needed to elucidate fully fruit’s role as a nitrogen source.