Abstract
The following ability of Marietta carnesi, a secondary parasitoid of diaspine scales, was suggested for host discrimination by investigation of materials collected from natural fields and laboratory experiments. The female of Marietta carnesi was able to distinguish between healthy Chrysomphalus bifasciculatus and those already parasitized by primary parasitoids, and selected the latter for oviposition. It was also capable of distinguishing between various developmental stages of the primary parasitoid, Comperiella bifasciata, developing within the secondary hosts, and selected scales containing pupae of the primary parasitoid for oviposition. Sometimes, however, it also deposited eggs on scales containing larvae of the primary parasitoid when densities of pupae of the primary parasitoid were decreased. Ovipositing females of Marietta were also able to distinguish between healthy pupae of Comperiella and its own species, avoiding autoparasitism. Finally, Marietta discriminated healthy pupae of Comperiella and those already parasitized by its own species, and avoided superparasitism. Nevertheless, superparasitism sometimes occurred when the densities of Comperiella were decreased.
