Peter G. VALEUR, Bill S. HANSSON and Christer LOFSTEDT
Department of Animal Ecology, University of Lund, S-223 62 LUND, Sweden
Adaptation habituation is proposed as one of the mechanisms behind mating disruption of male Lepidopterous males with sex pheromone. This mechanism can he divided in to two parts, sensory overload and sensory fatigue. We here investigate the sensory fatigue part of this mechanism. During 4-6 hours, Agrotis segetum Schiff. (Lepidoptera: Noctuidae) males were placed individually in Petri-dishes and exposed lo a range of different concentrations of (Z)-5-decenyl acetate, (Z)-7-dodecenyl acetate, (Z)-9-tetradecenyl acetate, (Z)-5-dodecenyl acetate, the complete 4-component sex pheromone and the non-pheromone component (Z)-4-dodecenyl acelale. We tested the effect of this preexposure on behaviour, e.g. flight up to a synthetic 4-componont bait in a wind tunnel. We also tested the effect on electroantennographic (EAG) responses. In control experiments, where the moths were preexposed to evaporated solvent, 55-70% of the tested males reached the source. Preexposure to the 4-component mixture or to (Z)-5-decenyl acetate reduced the wind-tunnel responses to <5%, at a preexposure level of 0.1 µg and 1 µg, respectively. Preexposure to 10 µg of (Z)-7dodecenyl acetate also reduced the response to <5%, while preexposure to the two other minor components only reduced the response to <20)% ay 100µg, the highest dose tested. Preexposure with 1µg of the 4-component mixture or the (Z)-5-decenyl acetate reduced the EAG response with 20-50%. The reduction was expressed as a generally lowered response to all single components as well as to the blend, even if preexposed to a single component. EAG-responses were considerably less reduced than behavioral responses at comparable levels of preexposure. This fact suggests that the hehavioural reduction was not only caused by peripheral adaptation, but also by a central habituation process. A comparison of these results with field studies in the literature suggests that sensory fatigue most probably did not explain any of the mating disruption effects found in field experiments.