Stereochemistry of Fuscumol and Fuscumol Acetate Influences Attraction of Longhorned Beetles (Coleoptera: Cerambycidae) of the Subfamily Lamiinae

Abstract

The chemical structures of aggregation-sex pheromones of longhorned beetles (Coleoptera: Cerambycidae) are often conserved among closely related taxa. In the subfamily Lamiinae, adult males and females of several species are attracted by racemic blends of (E)-6,10-dimethyl-5,9-undecadien-2-ol (termed fuscumol) and the structurally related (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (fuscumol acetate). Both compounds have a chiral center, so each can exist in two enantiomeric forms. Males of many species of longhorned beetles only produce one stereoisomer of each pheromone component, and attraction may be reduced by the presence of stereoisomers that are not produced by a particular species. In a previous publication, analysis of headspace volatiles of adult beetles of the lamiine species Astyleiopus variegatus (Haldeman) revealed that males sex-specifically produced (S)-fuscumol and (S)-fuscumol acetate. Here, we describe field trials which tested attraction of this species to single enantiomers of fuscumol and fuscumol acetate, or to blends of enantiomers. We confirmed attraction of A. variegatus to its species-specific blend, but during the course of the trials, found that several other species also were attracted. These included Aegomorphus modestus (Gyllenhall), attracted to (S)-fuscumol acetate; Astylidius parvus (LeConte), attracted to (R)-fuscumol; Astylopsis macula (Say), attracted to (S)-fuscumol; and Graphisurus fasciatus (DeGeer), attracted to a blend of (R)-fuscumol and (R)-fuscumol acetate. These results suggest that chirality may be important in the pheromone chemistry of lamiines, and that specific stereoisomers or mixtures of stereoisomers are likely produced by each species.

Keywords: Cerambycidae; chirality; enantiomer; pheromone; semiochemical.