Identification of host-plant chemicals stimulating oviposition by swallowtail butterfly,Papilio protenor.

The ovipositional response of a Rutaceae-feeding papilionid butterfly,Papilio protenor, toCitrus host plants was evoked by the synergistic action ofL-(-)-stachydrine,D-(-)-quinic acid, (-)-synephrine, andL-(-)-proline that characterize the chemical compositions of the leaves and epicarp ofCitrus plants (C. natsudaidai andC. unshiu). The stimulatory activity of their mixture was enhanced by the addition of flavanone glycosides, naringin and hesperidin, which coexist in these plants and have previously been demonstrated to serve as oviposition stimulants. However, sugars such as sucrose, glucose, and inositols, which abound in plant tissues, exerted no effect on egg-laying by the females. On the other hand, chlorogenic acid present in the leaves of another host plant,Fagara ailanthoides, was found to act as an excellent synergist. However, there existed significant qualitative dissimilarities between the chemical compositions of the leaves ofC. unshiu andF. ailanthoides. This strongly suggests thatP. protenor is likely to utilize different categories of compounds as chemical cues in recognizing each plant as a host.