Feeny 9700718 Ovipositing insects generally make final host-selection decisions on the basis of compounds present on the leaf surface. Little is known about the chemistry of leaf surfaces and how variation in surface-chemical profiles is related to host selection by insects. The goal of this project is to examine the leaf-surface chemistry of a single plant species (Daucus carota) with particular reference to compounds already identified as oviposition stimulants for one of its specialist insect herbivores (Papilio polyxenes). Plant surfaces will be extracted with a combination of chloroform and near-boiling water, and the resulting extracts fractionated and analyzed using high performance liquid chromatography. The project will include: (1) comparisons of the surface-chemical profiles of leaves differing in age, form, life history and genotype; (2) comparisons of the surface-chemical profiles of plants differing in acceptability as oviposition substrates; and (3) comparisons of larval performance on plant genotypes differing in oviposition acceptability. These experiments should determine the extent to which leaf-surface chemical variation is correlated with oviposition preferences of an insect species and subsequent larval performance. This research will reveal whether chemical signals on leaf surfaces can serve as keys for recognition of quality host sites by ovipositing female butterflies.
