Abstract
Drosophila melanogaster males from Canton-S and Oregon-R stocks perform more courtship in response to virgin females from the stock other than their own. Pairs of Canton-S and Oregon-R males also court each other more in the presence of volatile compounds extracted from Oregon-R and Canton-S females, respectively. These observations suggest that
D. melanogaster females are polymorphic with respect to some components of their sex pheromone system and that males are capable of distinguishing females from their own stock and females from another stock on the basis of these differences in pheromone production.