Role of contact pheromones in mate recognition in Xylotrechus colonus

Adult male and female rustic borers, Xylotrechus colonus F. (Coleoptera: Cerambycidae), aggregate on cut logs and fallen trees that are the hosts of their larvae. Our studies show that male X. colonus actively search for females, and only respond to them after contacting them with their antennae. Stripping cuticular hydrocarbons from females with solvent rendered them unattractive to males, suggesting that males did not recognize females by mechanoreception alone. Reapplying solvent extract to washed females restored their attractiveness to males, confirming the role of cuticular hydrocarbons in mate recognition. Female cuticular hydrocarbon extracts contain n-pentacosane, 9-methylpentacosane, and 3-methylpentacosane, components that were either absent or present in very small amounts on males. We demonstrate that the contact pheromone is a blend of these three cuticular hydrocarbons.