Populations of the Red Flour Beetle Tribolium castaneum (Coleoptera: Tenebrionidae) Differ in Their Sensitivity to Aggregation Pheromones

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Abstract
Male Tribolium castaneum (Herbst) produce an aggregation pheromone that attracts conspecific females. We used a two-choice pitfall trap to test the response of females from four laboratory populations to natural pheromone gathered from males of each population and to synthetic 4, 8-dimethyldecanal. Three populations were derived from animals collected 7 years ago: two in Spain and one in Yugoslavia. The fourth population had been in laboratory culture at Chicago for at least 30 years. In eight combinations of the two population choice tests, females did not discriminate between pheromone from their own population and from another population; in three of the four remaining combinations, females discriminated significantly against the stimulus from their own population. Females from the laboratory population and one Spanish population did not respond differently to different concentrations of synthetic 4, 8-dimethyldecanal. Females from the other Spanish population showed an increasing response with increasing concentration, and females from the Yugoslavian population responded most to an intermediate concentration. We discuss the possible chemical bases for these results, and their evolutionary implications.