Conditioning of leaf-shape discrimination by chemical cues in the butterfly, Battus philenor

In a large outdoor screened enclosure, female pipevine swallowtail butterflies (Battus philenor) were trained to search selectively for leaves of a shape similar to that of the Aristolochia host species to which they were exposed as adults. Conditioning was reversed by exposure to an alternative host species with a different leaf shape. Results indicated that contact with a host plant without oviposition was sufficient to induce a change in alighting responses to leaves of different shapes. Enclosure assays employing non-host species possessing leaves of different shapes and treated with host extracts demonstrated that females associate the shape of their alighting substrate with host chemicals present on the surface of that substrate. Results suggested that contact with host extracts without oviposition can induce changes in alighting responses to leaves of different shapes. A hypothesis is presented in which the primary host species for which females in an east Texas population learn to search varies seasonally with changes in host leaf chemistry.