The rôle of male and female pheromones in the mating behaviour of Tenebrio molitor

Abstract

At least one male and one female specific pheromone was found mediating the mating behaviour of Tenebrio molitor. The assay system used was a choice-chamber. The pheromone of the female stimulated the locomotor activity of the male and also mediated copulatory behaviour. In the absence of a female, a stimulated male may attempt to copulate with another male; this tendency was used to assay this pheromone. When live female lures were tested on groups of males, an average of 27 per cent of the males exhibited copulatory behaviour. When male lures were tested, this copulatory response was elicited in less than 2 per cent of the males. When female extracts were tested, the percentage of males which responded positively was dose dependent up to four female equivalents. There was little or no response to male extracts. The pheromone of the male stimulated the female's locomotor activity and the aggregation of females in the vicinity of the male or male extract. In response to a male lure, a significantly higher percentage of females became active and entered the central chamber than in the controls. This stimulation is dose dependent up to ten male equivalents. The second criterion used was the percentage of females which remained in the central chamber at the end of the 30 min observation period. A significantly higher percentage of females remained aggregated when a male rather than a female lure was tested. This effect was dose dependent up to five male equivalents. As no effect could be demonstrated with female extracts, the pheromone of the male also appears sex specific. The question of multiple male pheromones is discussed.