The importance of being yellow: visual over chemical cues in gender recognition in a social wasp

Differences in male and female phenotypes are often the results of sexual selection. Over the years, a vast number of studies investigated how and why the 2 sexes differ in their physical appearance, reaching the conclusion that peculiar visual traits, signals, or ornaments usually evolve under the pressure of sexual selection to mediate intrasexual competition and mate choice. In social contexts, however, males and females can hold different roles and social interactions may depend on the individual gender. The female-dominated hymenopteran societies represent a fascinating scenario to investigate recognition and communication among individuals of different genders outside a common sexual selection framework because sterile female workers typically do not mate and are not attracted to males. Here, we used laboratory bioassays (lure presentation experiments) to evaluate the ability of Polistes dominula workers to discriminate between individuals of the 2 genders, investigating the relevance of the chemical and visual cues potentially involved in such process. Our results showed that P. dominula workers are able to discriminate between the sexes and visual cues rather than chemical ones are responsible for such discrimination.