Real-time measurement of pheromone release from individual female moths and synthetic dispensers in a wind tunnel by recording of single receptor-neurone responses

Measurements of single neurone activity in the peripheral pheromone recepto rs of male Agrotis segetum (Denis & Schiffermuller) (Lepidoptera: Noctuidae ) were performed in a wind tunnel using a portable electrophysiological rec ording unit. Filter paper and rubber septa loaded with synthetic sex pherom one, as well as individual conspecific female glands, were used as pheromon e sources. Recordings, up to 3 h long, were analysed for temporal variation in spiking activity. The recordings were performed 2 m downwind of the sou rce, where the pheromone plume had a width of approximately 12 cm, as could be measured with the single cell preparations. The system allowed reliable measurements of relative pheromone concentration with a 20-s time resoluti on. The release rate from rubber septa loaded with pheromone was more or le ss constant over time, whereas the release rate from filter paper loaded wi th pheromone decreased to one tenth of the initial value within 6 min from the application of the pheromone. The release of pheromone from female pher omone glands was pulsed with an interval of 2-10 min between bursts. This p ulsing was not caused by retraction of the gland, as the glands were forcib ly extruded during the entire experiment, but should reflect variation in t ransport of pheromone to the gland surface and subsequent release. The demo nstrated stability of the preparations using tungsten electrodes, the relia ble monitoring of female-produced pheromone plumes at several metres distan ce, and the time resolution obtained are important steps towards field moni toring of natural pheromone plumes, as well as pheromone concentration and distribution in applications for mating disruption.