Abstract
Bioassay studies with mixtures of the two components from the sex pheromone ofE. postvittana are used to construct a dose-response surface. The surface clearly shows the existence of a response maximum and that an optimum ratio of the two components applies over a wide range of concentrations. Probit transformations of the same data are used to construct an isobologram. The isobole has a sharp minimum at a ratio for the two components close to the ratio produced by the females.