none Aphidius ervi; Aphidius microlophii; MATING-; LONGEVITY-; Hybridization influences & implications for evolutionary isolation; EVOLUTIONARY-ISOLATION; Pre & post mating isolating mechanisms investigation Aphidius microlophii x A. ervi; HYBRIDIZATION-; Longevity effects & parental species evolutionary isolation relationships The present study aims at evaluating the occurrence and the importance of some pre-mating and post-mating isolation mechanisms, preventing gene flow between Aphidius ervi Haliday and Aphidius microlophii Pennacchio & Tremblay (Hymenoptera, Braconidae). Mating experiments were carried out in choice conditions by keeping in contact for 5 days a male with two females, of which one was conspecific. Mating occurrence was assessed by examining the content of the spermatheca of both females. Data analysis was performed by calculating the Charles-Stalker Isolation Index. The longevity of the hybrids, obtained by crossing A. ervi females with A. microlophii males, was evaluated and compared to that of both parental lines. The occurrence of heterogamic matings was almost completely prevented by the existence of strong ethological barriers. The isolation index calculated for A. ervi and A. microlophii males were 0.82 and 0.60 respectively, both significantly different from 0, which denotes random mating. Longevity was significantly affected by sex and food, and was significantly lower in the hybrid females. These data, along with others from previous studies, further support the status of separate species proposed for these two parasitoid populations.