Exposure to the plant compound alpha-humulene reduces mating success in male Mediterranean fruit flies

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), displays lek mating where searching females actively choose among aggregated males that produce visual, acoustic, and olfactory signals within the tree canopy. Recent studies demonstrated that treated males exposed to the aroma of particular plant compounds (α-copaene) or oils (orange, manuka, and ginger) gain a mating advantage over control, non-exposed males. The goal of this study was to assess the impact of another plant compound, α-humulene, on the mating success of male C. capitata. Prior work showed that α-humulene was not attractive to either sex but elicited a strong electroantennal response in males. Field cage tests showed that males exposed to the aroma of α-humulene obtained significantly fewer matings than control (non-exposed) males as long as 3 d following exposure. Exposed males exhibited lower signaling (pheromone calling) activity than control males, which presumably contributed to their reduced mating success. Despite this lessened activity, the mortality of treated males after chemical exposure was similar to that observed for control, non-exposed males, suggesting that α-humulene was not a toxic or severely debilitating agent.