Two compounds, (E)-11-tetradecen-1-yl acetate and (E,E)-9,11-tetradecadien-1-yl acetate, have been identified in extracts of females of the lightbrown apple moth,Epiphyas postvittana (Walker). The two compounds are active as a coalitive pair and are present in extracts of females in a ratio of about 20∶1.

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The degree of reduction in sex pheromone mediated responsiveness of male light-brown apple moth which is brought about by previous brief exposure to the pheromone is related to the concentration of that pre-exposure, and hence to the level of excitatory sensory input generated by it.We have shown previously (Bartell and Lawrence 1973) that the responsiveness of males of the lightbrown apple moth, Epiphyas postvittana (Walker), to female sex pheromone was reduced by previous exposure to it, even when there was a 5 h interval between the initial exposure to the pheromone and the subsequent bioassay test. In earlier experiments we investigated the effects of the duration of the preexposure and the interval between pre-exposure and bioassay, but did not investigate the effects of different concentrations of pheromone. A trial in which males received pre-exposure to different concentrations of pheromone is the subject of this note.All conditions regarding rearing and photoperiodic entrainment of the moths, ambient temperature and light intensity at the time of pre-exposure and of bioassay, the apparatus used and the experimental procedures employed were as reported in our earlier paper (Bartell and Lawrence op. cit.). Crude extracts of female abdomen tips were used as the pheromone source for both pre-exposures and subsequent bioassay, the quantity of sex pheromone present being expressed in female equivalents (F.E.).Pre-exposures were of 10 min duration and the interval between the end of this period and the start of bioassay was SO min, during which pheromone-free air was passed over the males. During pre-exposure