Abstract: The process of ovipositional behaviour of Trichogramma ostriniae Pang et
Chen was divided into four major stages: drumming, drilling, oviposition and
withdrawal of ovipositor. The duration of each stage on different host eggs were differed. The oviposition of female and male eggs are behaviorally distinct processes. The number of progeny allocated to a host varied according to the size of the host egg, generally, 1 and 2 in the Sitotrog a cerealella and Ostrinia nubilalis eggs, respectively. Significan tdifference were found in acceptance of parasitized host eggs between experienced and inexperienced T. ostriniae females. The capability of discriminating between the parasitized and non-parasitized host eggs can be obtained through 'learning' . T. ostriniae female can discrim inate self-and conspecific-parasitized eggs. T. evanescens also can detect the previously parasitized host by T. ostriniae toavoid conspecific-superparasitisim.