D3212: The phenology of pheromones: Understanding mating behavior in an unlighted firefly species

Mating behavior in insects is often mediated by chemical communication, utilizing pheromones that are recognized by odorant receptors (ORs), allowing for olfactory signals to trigger a neural and behavioral response in organisms. However, open questions remain about the phenology of olfactory response in many insect lineages. The winter firefly (Photinus corruscus), a day-active unlighted firefly species that emerges from pupation in the fall, overwinters as an immature adult, and matures its gonads and mates in the spring. Recently our lab identified a female-emitted compound, hydroxycamphor, as the sex-attractant pheromone in the P. corruscus. Here, we document the phenology of sex-attractant pheromone response of winter firefly males emerging from winter diapause. We compared numbers of males captured in pheromone-baited versus control (solvent-only) live traps monitored weekly at one site in Pennsylvania over a period of 19 weeks, while also documenting the presence of winter fireflies in the environment neighboring the traps. We found that, despite their presence and activity in the environment, males were not attracted to pheromone-baited traps until mid-April. This suggests that males are not developmentally ready to respond to pheromone until later in the spring and that some environmental and/or physiological cue stimulates the development of pheromone response as males emerge from diapause. This result establishes a foundation for studying the basis of seasonal differences in pheromone response from molecules to development.