Discrimination of mixtures of female sex pheromone components by male Trichoplusia ni (Hubner)

Pheromone mixture discrimination by male cabbage loopers, Trichoplusiani (Hübner), was assessed in a wind tunnel by responsedifferences to paired stimuli. They discriminate differencesbetween mixtures that contain three and all six of the pheromonecomponents that are emitted by virgin females. The ability todiscriminate between these two mixtures is perplexing becauseonly three antennal pheromone specialist neurons respond atnatural stimulus intensities. The cabbage looper also discriminatedbetween mixtures whose component ratios differed slightly fromthat of the female. There was some interaction between the stimulusintensity, the distance between the stimulus sources, and possiblythe extent of the perceptual difference. The mixtures of pheromonecomponents failed to enhance the amount of upwind flight responseover that of Z7–12:Ac alone. Other evidence argues thatthe instantaneous release of pheromone may exceed time-averagedmeasures.