Abstract
Paraulax Kieffer and Cecinothofagus Nieves-Aldrey & Liljeblad (Cynipidae: Paraulacini) were long supposed to be gall-makers on southern beeches ( Nothofagus , Nothofagaceae). Dissections of galls on Nothofagus Blume, suggested that Cecinothofagus could be instead either endoparasitoid or inquiline of Aditrochus larva (Chalcidoidea). We sequenced the universal COI barcode and Ultra-Conserved Elements (UCEs) from young larvae of Aditrochus collected from galls on Nothofagus and highlighted that one of them also contained DNA from Cecinothofagus ibarrai Nieves-Aldrey & Liljeblad. So far, when galls attributed to Aditrochus were dissected in early development stages they all contained only a single larva and no remains of other larvae. Conversely, when Cecinothofagus ibarrai was reared from galls on Nothofagus , remains of the host larva were observed inside the larval chamber. Altogether, biological observations and molecular results suggest that Cecinothofagus ibarrai is likely an endoparasitoid of Adritrochus . This result confirms the tribe Paraulacini as being entomophagous and supports the hypothesis of an ancestral parasitoid lifestyle for Cynipoidea.