Study of the performance of an oophagous parasitoid Ooencyrtus pityocampae (Mercet) (Hymenoptera: Encyrtidae) to fight against Mediterranean ecosystem pests. Description of the subject. As part of a biocontrol program of the pine processionary, Thaumetopoea pityocampa Denis & Schiffermüller, the use of indigenous parasitoids to fight against this pest was studied in the UEFM Biocontrol Laboratory at INRA PACA. Objectives. Firstly, a focus was placed on the rearing of indigenous parasitoids, in order to be able to test them at different experimental scales. More specifically, the species Ooencyrtus pityocampae (Mercet) was studied. Method. Thaumetopoea pityocampa is allergenic; so, several substitute hosts were compared in order to rear pine processionary parasitoids: Philosamia ricini (Danovan), Nezara viridula (L.) and Halymorpha halys (Stål). Biological characteristics and descendants' fitness were compared in laboratory conditions (25 ± 1 °C, 75 ± 5% HR, 16L: 8D). Results. Philosamia ricini was found to be the best host among these three substitute hosts because it gave the best productivity and the best parasitoid quality. Conclusions. This study will help us to consider possibilities for the use of this parasitoid for the biological control of Mediterranean pests.