The ability of the encyrtid Ageniaspis citricola Logvinovskaya, a polyembrionic parasitoid of the citrus leafminer (Phyllocnistis citrella Stainton), to distinguish unparasitized hosts from those previously parasitized by the same female or by a conspecific was investigated. All the phases of the oviposition behavior of the parasitoid were observed and their sequence and duration recorded. Experienced and inexperienced A. citricola females were studied using P. citrella eggs laid on citrus leaves and two different host densities (2 and 20 eggs). The data revealed that experienced females are able to discriminate between unparasitized hosts and hosts previously parasitized by themselves as well as by a conspecific, despite the number of eggs at their disposal. Females that had never oviposited in unparasitized hosts (inexperienced) showed a higher rate of superparasitism; the possible factors inducing this behavior are discussed.