Peripheral and behavioral plasticity of pheromone response and its hormonal control in a long-lived moth

Reproductive success in many animals depends on the efficient production of and response to sexual signals. In insects, plasticity in sexual communication is predicted in species that experience periods of reproductive inactivity when environmental conditions are unsuitable for reproduction. Here, we study a long-lived moth Caloptilia fraxinella (Ely) (Lepidoptera: Gracillariidae) that is reproductively inactive from eclosion in summer until the following spring. Male sex pheromone responsiveness is plastic and corresponds with female receptivity. Pheromone response plasticity has not been studied in a moth with an extended period of reproductive inactivity. In this study, we ask whether male antennal response and flight behavior are plastic during different stages of reproductive inactivity and whether these responses are regulated by juvenile hormone. Antennal response to the pheromone blend is significantly reduced in reproductively inactive males tested in the summer and autumn as compared with reproductively active males tested in the spring. Reproductively inactive autumn but not summer males show lower antennal responses to individual pheromone components compared with spring males. Treatment with methoprene enhances antennal response of autumn but not summer males to high doses of the pheromone blend. Behavioral response is induced by methoprene treatment in males treated in the autumn but not in the summer. Plasticity of pheromone response in C. fraxinella is regulated, at least in part, by the peripheral nervous system. Antennal and behavioral response to pheromone differed in reproductively active and inactive males and increased with methoprene treatment of inactive males.