Metaphycus flavus (Howard) (Hymenoptera: Encytidae) is a facultative gregarious parasitoid of different soft scales (Hemiptera: Coccidae) including brown soft scales, Coccus hesperidum L. Superparasitism by this species and its consequences for immature parasitoids were studied. M. flavus females recognized the host by probing it with the ovipositor. Experienced and inexperienced females could discriminate against previously parasitized hosts from four hours to four days later. They also distinguished between scales attacked by themselves or by other four hours later but not two and four days after the first oviposition. M. flavus discriminated against scales containing at least one very young larva or scales containing only encapsulated eggs. Also, M. flavus practiced ovicide. They used the presence of egg stalks to detect the eggs laid previously, using their ovipositor to destroy the eggs inside the scale. Mortality rates of both clutches in the superparasitized scales were lower than the control (only parasitized scales) only when the second wasp superparsitized four hours later than the first but not two and four days later. The second clutch was in disadvantage because they suffered from competition with the parasitoids already present in the host, when superparasitizing two or four days later.