The analysis of variation in pheromone systems within and between populations of the same species would constitute a considerable contribution to the understanding of the role of pheromones in reproductive isolation. Breeding experiments which test the assortment of different types of pheromones and receptors could be especially useful.
The hypothesis presented in this chapter that differences in pheromone systems of closely related species may result from disruptive selection could be tested by monitoring mixed colonies of cross attractive species for changes in the propensity for interspeciﬁc mating. It would also be interesting to monitor population levels in mixed colonies to determine whether inviable interspeciﬁc mating can result in the extinction of one or both of the species.
We acknowledge with deep appreciation the constructive reviews of the manuscript by Richard S. Beal, Graduate Dean at the University of Northern Arizona, Flag- staff; Theodore T. Kozlowski, Professor of Forestry at the University of Wisconsin, Madison; and Robert M. Silverstein, Professor of Ecological Chemistry at the Col- lege of Environmental Science and Forestry, Syracuse, N. Y. We are also grateful to numerous additional colleagues for their contribution to the conceptual framework of this chapter and for their permission to cite unpublished reports or manuscripts in press.