Female arctiid moths, Utetheisa ornatrix, orient towards and join pheromonal choruses

In most moth species, pair formation has been characterized by female signalling with long-distance sex pheromones and male olfaction and orientation to these pheromones, followed by courtship. However, recent neurophysiological and behavioural evidence from some species indicates that females are not necessarily noninteractive signallers in the pair-forming process. In the arctiid moth, Utetheisa ornatrix, females establish pheromonal choruses in which they mutually influence one another to synchronize and intensify their signalling at dusk. In the present study, we investigated whether chorusing females modify their spatial dispersion as well. We report laboratory bioassays showing that female U. ornatrix move, orient and aggregate in response to signalling females, whole gland extract of the female sex pheromone, and several of the individual pheromone components. These activities are comparable to those shown by males in response to the female pheromone, although males may have greater sensitivity. We suggest that similar mechanisms underlie both male and female responses, and we discuss several hypotheses that may account for evolution of the female responses.