First Record of the Gall-Inducing Insect Ophelimus mediterraneus Borowiec & Burks (Hymenoptera, Chalcidoidea, Eulophidae) in Eucalyptus from America, Including the First Report of Male Specimens.

The invasive eucalyptus gall wasp Ophelimus mediterraneus Borowiec & Burks (Hymenoptera: Eulophidae) is reported for the first time in Argentina and the Americas, representing a new record on Eucalyptus benthamii, E. viminalis, and E. cinerea, thereby expanding its known host range. Species identification was supported by molecular analyses (mitochondrial COI and nuclear 28S gene sequences), adult morphology, and morpho-anatomical examination of the induced galls. The galls are small, circular to slightly ellipsoid protrusions usually located on one side of the leaf blade. Mature galls measure approximately 0.8-1.2 mm in diameter and contain a single larval chamber. They are monothalamous, with a central chamber lined with nutritive tissue and surrounded by a sclerenchymatic layer. Additionally, this study provides the first description of the male O. mediterraneus, including detailed morphological traits, biological observations, and illustrative images. Males were consistently present in all samples collected, suggesting that O. mediterraneus may reproduce sexually under certain environmental or ecological conditions. These findings highlight the urgent need to monitor the potential spread and impact of this exotic gall-inducing pest on regional eucalyptus plantations and emphasize the importance of integrating both morphological and molecular tools for accurate detection and assessment.