The Pine Processionary, Thaumetopoea pityocampa Denis & Schiffermüller, (Lepidoptera: Thaumatopoeidae) is the most damaging pest of pine trees in the Mediterranean region. Ooencyrtus pityocampae (Mercet) is a polyphagous egg parasitoid, known mainly as an egg parasitoid of the Pine Processionary. Studies were conducted to assess the biological parameters of this parasitoid on the new factitious host Philosamia ricini Danovan (Lepidoptera: Saturniidae) under laboratory conditions. Parasitism of P. ricini eggs by O. pityocampae is influenced by host egg age, number and age of the female parasitoid. To evaluate the effect of egg age of host and age of female parasitoid, groups of 50, 60, 80, 100 eggs of (1-2) and (3-4) days old were expose to 1, 3 and 5 days old age, for one or two female parasitoid. Then the parasitized eggs were incubated at 25°C ±1, R H 65%±5 and L:D 16:8 h photoperiod. As results, higher percentage of adult O. pityocampae emergence was obtained on (1-2) days old age P. ricini eggs. Emergence rate was affected positively by the parasitoid age. Fifty host eggs and five days old age one female parasitoid was more suitable for the economic and effective mass production programme. Developmental period of adult parasitoid was not affected by the host age. Longevity was significantly higher for parasitoid fed with bio-honey. Mass rearing of parasitoids is an essential step for biological control programs. Based on the results of this study, P. ricini is an appropriate host species for the mass rearing of O.pityocampae.