The male swallowtail butterfly, Papilio polytes, uses cuticular hydrocarbons for mate discrimination

Abstract

Many species of insects have sex-specific and species-specific cuticular lipid profiles that help regulate mate recognition and courtship behaviour. However, in adult butterflies, little is known about cuticular hydrocarbons (CHCs), the main component of the lipid profile, and their function in mating. Here, we investigated whether Papilio polytes males use cuticular lipids and major CHCs in mate discrimination. When males were presented with freshly killed female and male specimens, copulation attempts were more frequent after contact with the females. Upon removal of the cuticular lipid with solvent washes, the ratios of copulation attempts were similar for both male and female specimens. When male or female cuticular lipid extracts of P. polytes or Papilio protenor (a sympatric and related species) were applied to washed female specimens, males displayed less interest in specimens treated with extracts other than that of the conspecific females. Chemical analysis of the extracts revealed that the CHC profiles, especially the C23–C25 range, differed greatly between the sexes of the two species. Of the identified major hydrocarbons, authentic chemicals 7-tricosene (characteristic of P. polytes males) and 9-pentacosene (characteristic of P. protenor females) greatly reduced the ratio of male copulation attempts with the treated female models. Hence, P. polytes males use the CHC profile of their partner for mate discrimination, and particular alkenes probably play important roles in the prevention of interspecific and same-sex courtships.