Ethyl 4-methyl heptanoate: a male-produced pheromone of Nicrophorus vespilloides

Sexually mature male beetles of the genus Nicrophorus (Coleoptera: Silphidae) exhibit a conspicuous behavior, recognized as pheromone-releasing activity. Laboratory and field studies demonstrated that females are attracted to males that exhibit this behavior, both on or off reproductive resources. Here, we report the results of a study in which volatile chemicals released by calling Nicrophorus vespilloides were collected by solid-phase microextraction and analyzed by using coupled gas chromatography-mass spectrometry. These analyses revealed that ethyl 4-methyl heptanoate and (E)-geranylacetone are emitted by males that engage in the behavior. In the field, traps baited with racemic ethyl 4-methyl heptanoate caught roughly equal numbers of male and female N. vespilloides. Some male and female Nicrophorus vespillo and male Nicrophorus humator were also caught in traps baited with this compound. Traps baited with (E)-geranylacetone did not catch significant numbers of beetles.