Papilio polyxenes, the eastern black swallowtail butterfly, is a specialist on members of the carrot family, Apiaceae. Females choose food plants for their larvae, laying eggs singly on acceptable host plants, which vary considerably visually and chemically. To allow for fidelity of these vagile females to a single family of host plants in the absence of information transfer across life stages, the response to at least one type of host plant cue, be it visual or chemical, must be innate. Although much work has been done to identify the plant chemicals used by ovipositing swallowtails to recognize their host plants after landing, it has been assumed rather than demonstrated that the response to this cue is innate. We conducted two experiments to test the nature of the black swallowtail's response to contact chemical host plant cues, and a third to examine the role of the larval host plant in adult behaviour. The results of the first experiment verified that females without host plant experience respond specifically to cues from the host plant, Daucus carota, with typical abdomen curling, and not to the nonhost fava bean, Vicia faba. The nondeterrency of bean was also verified. The second experiment demonstrated that this response was unaltered by specific host plant experience: females responded to extracts of hosts, carrot and poison hemlock, Conium maculatum, differentially, but without regard to the plant previously experienced. We also examined effects of deprivation and age in the first experiment, with each having a significant effect; these were controlled for in the second experiment. Finally, feeding on a host plant as a larva did not increase the preference for that plant as an adult. This is the first demonstration that the response to these contact chemical cues is not only innate but unaltered by specific host plant experience.