Hesperophylax occidentalis (Trichoptera: Limnephilidae): Electroantennogram structure-activity study of sex pheromone component 6-methylnonan-3-one.

Electroantennogram (EAG) analyses ofHesperophylax occidentalis male and female antennae were used to generate dose-response curves for synthetic, racemic 6-methylnonan-3-one and to demonstrate the chemical specificity of male antennal olfactory cells. Male antennae responded to 6-methylnonan-3-one, the main female pheromone component. Females also demonstrated a response to 6-methylnonan-3-one, but a smaller one than males. The chemical specificity of male antennal receptors was determined by comparing EAG activity of synthetic, racemic 6-methylnonan-3-one and a series of structural analogs. The three structural parameters considered, including keto position, chain length, and methyl-group position, were demonstrated to contribute significantly to the reception of synthetic, racemic 6-methylnonan-3-one by male antennae. For straight-chain nonanones with keto groups at different positions, nonan-3-one elicited the greatest EAG responses from male antennae. For straight-chain alkan-3-ones with different chain lengths, the EAG responses of male antennae to nonan-3-one and decan-3-one were the same, but greater than those to other chain lengths. For methyl-branched nonan-3-ones, 6-methylnonan-3-one elicited greater EAG responses from antennae than analogs with the methyl group at another position.