A pulsed cloud of sex pheromone elicits upwind flight in male moths

ABSTRACT. Male oriental fruit moths do not fly upwind in a continuous uniform cloud of pheromone, but readily do so when the cloud is pulsed at 1 or 0.5/s or when a plume from a point source of pheromone is placed within the continuous cloud. It is suggested that males of moth species that require such fluctuating pheromone stimulation for upwind flight will normally receive it from a filamentous, point-source-produced plume. However, we hypothesize that upwind progress may cease close to the source due to excessively high emission rates or inappropriate blend ratios, when fluctuating sensory output becomes attenuated, despite higher actual molecular concentration fluctuations.