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

Abstract

Pheromone mixture discrimination by male cabbage loopers, Trichoplusia ni (Hübner), was assessed in a wind tunnel by response differences to paired stimuli. They discriminate differences between mixtures that contain three and all six of the pheromone components that are emitted by virgin females. The ability to discriminate between these two mixtures is perplexing because only three antennal pheromone specialist neurons respond at natural stimulus intensities. The cabbage looper also discriminated between mixtures whose component ratios differed slightly from that of the female. There was some interaction between the stimulus intensity, the distance between the stimulus sources, and possibly the extent of the perceptual difference. The mixtures of pheromone components failed to enhance the amount of upwind flight response over that of Z7–12:Ac alone. Other evidence argues that the instantaneous release of pheromone may exceed time-averaged measures.