Subtleties in perception and discrimination by cabbage looper moths, Trichoplusia ni, of the two 14-carbon acetate sex pheromone components

Three compounds that are emitted by virgin female cabbage looper moths, Tri choplusia ni, (Z)-7-dodecenyl acetate (Z7-12:Ac), (Z)-7-tetradecenyl acetat e (Z7-14: Ac), and (Z)-9-tetradecenyl acetate (Z9-14: Ac), are detected by antennal olfactory receptor neurons specialized to detect sex pheromone com ponents. The principal evidence signifying that either or both of Z7-14:Ac and Z9-14:Ac have an effect on male behavior comes from an observed reducti on in the numbers of males trapped by Z7-12:Ac paired with a six-component mixture. The evidence conforms to a hypothesis that either or both of these compounds are the basis for discrimination between the two mixtures. Howev er, scant evidence for this hypothesis was obtained in paired-source labora tory wind-tunnel assays, even at airborne concentrations of Z7-14:Ac and Z9 -14:Ac that ranged up to 1000x that emitted by a female. Furthermore, there was little evidence from single-source laboratory or field trap assays con firming that Z7-14:Ac and Z9-14:Ac at or above natural stimulus strengths m odify the moth's perception of Z7-12:Ac. The data suggest that discriminati on of small mixture differences may not be resolvable within the confines o f a wind tunnel.