Telenomus californicus Ashmead is a major egg parasite of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), throughout the host's range. This parasite is effective at finding host egg masses. Even when host insects are sparse, over 90% of egg masses may be attacked and 50% of the total egg complement destroyed (R.R. Mason and T.R. Torgersen, unpub.). In the southwest an undetermined Tetrastichus species can also be a significant egg parasite of the tussock moth. Because host finding might involve some degree of kairomonemediated behavior we were interested in any effect that synthetic pheromone, applied to disrupt mating of the host, might have on parasitism by these valuable species.