The age ofTrichogrammaparasitoids could influence biological traits which are of great importance for effectiveness of mass rearing systems. Recent studies demonstrated thatTrichogramma ostriniae(TO) could parasitizeAntheraea pernyieggs through multiparasitism along with other Trichogrammaspecies, although few adults could emerge successfully. It is important to characterize the factors modulating the performance of TO onA. pernyieggs, notably in order to try enhancing its quantitative emergence through multiparasitism for further use in biological control. In this context, irrespective of host age, we tested different ages of TO females (from 0.5-day- to 6-day-old postemergence) in multiparasitism withTrichogramma chilonis(TC) onA. pernyieggs. The results of the present study confirmed that TO parasitism onA. pernyieggs was largely age dependent. Higher percentage of multiparasitism and higher number of emerged TO adults were recorded in the treatment where 3-day-old TO females were used for parasitization with TC onA. pernyihost. In addition, we also tested different female ratios of bothTrichogramma species to find out an optimal ratio for use in mass production. The highest percentage of multiparasitism, emergence and optimum emerged number of TO (perA. pernyiegg) was observed with the ratio 3:2 (TO:TC) per 1 host egg. This study demonstrated that the age of TO females can significantly affect their performance in multiparasitism of largeA. pernyieggs. These results prompt for more research in order to develop an effective multiparasitism-based production of TO at the industrial scale.