Chemical basis for differential acceptance of two sympatricrutaceous plants by ovipositing females of a swallowtailbutterfly, Papilio polytes (Lepidoptera, Papilionidae)

Summary. In the natural habitat of Papilio polytes, aRutaceae feeder utilizing Toddalia asiatica as a major host plant, some other rutaceous plants such as Murraya paniculata(abundant) and Glycosmis citrifolia (relatively rare)occur sympatrically as potential hosts. WhereasG. citrifolia is occasionally infested in the field, M. paniculata remains entirely unexploited by the butterfly. We thus examined thephytochemical mechanisms that can explain the differentialacceptance of the two plants by ovipositing females ofP. polytes. The foliage of G. citrifolia was found to readilyinduce oviposition and females deposited eggs in responseto a methanolic extract of the plant. Stimulatory activity-directedfractionation of the extract revealed the presence oftwo characteristic compounds, trans-4-hydroxy-N-methylprolineand 2-C-methylerythronic acid, known to serve asoviposition stimulants for the butterfly. In addition, larvaeperformed as well or better onG. citrifoliaas on T. asiatica.Similar examination of the inhibitory chemical constituentsof M. paniculata led to the isolation of an oviposition deterrent. The compound, identified as trigonelline (N-methylpyridine-3-carboxylic acid), exhibited moderateoviposition deterrency to females. These results combinedwith our previous data are in agreement with the observeddifferential utilization of the two plants byP. polytes in the field.