Aristolochiaceae‐ and Asteraceae‐feeding by larvae of Papilio xuthus L. (Lepidoptera: Papilionidae) in Japan: A review

Abstract

AbstractOur recent observations of Aristolochiaceae‐ and Asteraceae‐feeding by larvae of Papilio xuthus L. (Lepidoptera: Papilionidae), which is generally a typical Rutaceae‐feeding swallowtail, inspired us to survey published works describing its host range and aspects of its chemical ecology. Papilio xuthus larvae have been observed feeding on a total of 22 plant species other than members of Rutaceae, including those of Asarum (Aristolochiaceae) and Cosmos (Asteraceae). Most observation records and our current study indicated that Aristolochiaceae‐feeding by P. xuthus larvae was not due to oviposition error, but to larval movement to Asarum from adjacent rutaceous hosts after they had become unsustaining. Many larvae developed on Asarum to further stadia but we confirmed that some did not, indicating that Asarum was unsuitable for some individuals. According to previous and current observations, P. xuthus females oviposit directly on Cosmos and their larvae can develop to adults although, again, their performance on these plants is not always favorable. Host choice by swallowtail butterflies is determined both at the egg‐laying and larval‐feeding stages. Although adult P. xuthus use a mixture of unique secondary metabolites as their host‐location cue, larvae use primary nutrients as their major phagostimulants. Larval feeding on Asarum could suggest a reversion triggered by vestigial chemosensitivity to ancestral olfactory and/or gustatory cues, because several major clades of Papilionidae feed on Aristolochiaceae. Further studies on the phytochemical/chemosensory bases for these associations are needed if we are to understand the evolutionary pathway of host selection in P. xuthus, as indicated by these relatively unusual host‐seeking behaviors.