FACTORS INVOLVED IN HOST DISCRIMINATION BY EPIDINOCARSIS-LOPEZI AND LEPTOMASTIX-DACTYLOPII (HYM, ENCYRTIDAE)

The factors involved in host discrimination by two Encyrtid Hymenopter a, Epidinocarsis lopezi and Leptomastix dactylopii, parasitoids of the mealybugs Phenacoccus maniboti and Planococcus citri (Pseudococcidae) respectively, were compared in a behavioural study. Females of both s pecies can discriminate between unparasitized and parasitized hosts wh atever the time elapsed since first oviposition. Discrimination is bas ed on several stimuli which act either simultaneously or successively. In E. lopezi, the rejection of parasitized hosts occurred either afte r a simple antennal contact, as a result of the defense behaviour of t he parasitized host, or after the insertion of the ovipositor. In the latter the parasitoid probably detects a modification in the compositi on of the haemolymph due to the presence of the developing parasitoid. In L. dactylopii, parasitized hosts were rejected mainly after antenn al palpation, the possible markers identified being either an external pheromone or the physical marker provided by the egg stalk emerging f rom the surface of the parasitized host. After 3 days of infestation, the use of the ovipositor is sometimes necessary.