Contribution of Sex Pheromone to Mate Location and Reproductive Isolation in Aphid Species (Homoptera: Aphidinea)
Some 20 years ago it was clearly demonstrated that female of the bisexual generation (Sx-female) produce sex pheromones which are released from scent plaques on the metathoracic tibiae and detected by sensory cells of the secondary rhinaria on male antennae. The pheromones appeared to be active only at very short distances and, as cross-species responses were observed, they did not appear to be species specific. Recently the sex pheromones of a number of aphid species have been chemically characterized as specific isomers of the monoterpenoids, nepetalactol and nepetalactone, which are released in species-specific blends. This development, together with chemical synthesis of the compounds, has allowed the investigation of synthetic pheromone activity in both the laboratory and the field. Olfactometer and mating bioassays reveal that male are maximally responsive to synthetic pheromone mixtures close to their natural blends but that interactions between species do occur. Field trials have revealed that flying male can be attracted to sex pheromone lures in a species-specific manner. The present paper reviews the role of mate location and reproductive isolation in Aphididae with emphasis on sex pheromone and these latest findings.