Identification of A Sex Attractant Pheromone for the North American Click Beetle Elater abruptus (Coleoptera: Elateridae).

Of the > 1000 known species of North American click beetles (Coleoptera: Elateridae), sex pheromones have only been identified from a handful of species. Here, we report the identification of 5-methylhexyl (Z)-4-decenoate as the female-produced pheromone of the elaterid Elater abruptus Say (subfamily Elaterinae), a species native to the northeastern United States. The pheromone was species-specific in the geographic region where it was tested, attracting only males of the target species. Ovipositor extracts contained a number of related esters, but only two, hexyl (Z)-4-decenoate and 5-methylhexyl (Z)-4-decenoate, elicited responses from antennae of male beetles in coupled gas chromatography-electroantennogram assays. In a field experiment, traps baited with 5-methylhexyl (Z)-4-decenoate, and those baited with the blend of that compound and hexyl (Z)-4-decenoate, captured significantly more beetles than did control traps. Hexyl (Z)-4-decenoate as a single component did not attract significant numbers of beetles. This phenomenon of the production of a number of inactive analogs and homologs of a pheromone component has been reported previously for a number of other elaterid species, and it remains unclear what purpose these apparently redundant compounds may serve.