Department of Entomology, University of California, Riverside, CA 92521, USA.
Several species of saturniid moths in the genus Hemileuca occur in the mountains and deserts of the southwestern United States. The larvae of these moths feed on native vegetation in habitats that are largely undisturbed, and the distributions of the Hemileuca species represent the natural result of evolution, as opposed to the artificial distributions of many insect species that have occurred as a result of human activities. The pheromone blends of these moth species consist primarily of blends of 10,12-hexadecadienyl aldehydes, alcohols, and acetates. Recent work has shown that the pheromone systems of different populations of a single species exhibit marked variation in 1) the pheromone blend produced by female moths, 2) the antennal response profile of male moths, and 3) the behavioral responses of males from different populations to a particular pheromone blend. The differences between populations appear to correlate with the presence or absence of sympatric congeners that share some or all of the same pheromone components. The shifts in the female-produced pheromone blends and the male behavioral and antennal responses may represent reproductive character displacement to avoid interference in pheromone-mediated reproductive behaviors. The evidence in support of a case for reproductive character displacement will be presented.