Male-produced aggregation pheromone of the maize weevil,Sitophilus zeamais, and interspecific attraction between threeSitophilus species.

A dual-choice pitfall bioassay was used to demonstrate the existence of a male-produced aggregation pheromone in the maize weevil. Both males and females showed a highly significant preference for extracts of disks exposed to wheat-feeding males over extracts of disks exposed to wheat kernels only. Neither sex responded significantly to extracts from females. Mating did not reduce pheromone release by males. Response by virgin females to pheromone was significantly higher than response by mated females, but males of either mating status responded equally well. There was no apparent daily periodicity in the responsiveness to pheromone. Rice and maize weevils showed a strong interspecific cross-attraction. Granary weevils of both sexes responded well to maize weevil extracts, but only females showed a significant response to rice weevil extracts. Neither maize nor rice weevils responded significantly to granary weevil extracts.