Kfir, R., Department of Entomology, Faculty of Agriculture, Hebrew University, Rehovot, Israel
Rosen, D., Department of Entomology, Faculty of Agriculture, Hebrew University, Rehovot, Israel
Podoler, H., Department of Entomology, Faculty of Agriculture, Hebrew University, Rehovot, Israel

Competition tests were carried out in the laboratory among the hyperparasitic wasps Cheiloneurus paralia, Marietta javensis and Pachyneuron concolor, developing upon the primary parasite Microterys flavus in the brown soft scale. In single-species experiments Marietta was the most efficient; it eliminated the population of the host whereas Cheiloneurus and Pachyneuron were not able to do so. In 2-species experiments Marietta completely replaced Cheiloneurus within 6 weeks and Pachyneuron within 8. Cheiloneurus replaced Pachyneuron within 20 weeks. In 3-species experiments Cheiloneurus was eliminated within 4 weeks and Pachyneuron within 9. During the course of all experiments the mortality rate of immature parasites and hyperparasites increased, and progressively more cells failed to give rise to either an adult Microterys or a hyperparasite. This was due to host feeding and superparasitism. Pachyneuron was able to use Cheiloneurus as a host but not vice versa. The superiority of Marietta may be partly due to the fact that it is capable of utilizing its competitors as hosts, whereas they cannot develop upon it. © 1983 Springer-Verlag.