There are no known troglobiotic hymenopterans, although a few species regularly occur in caves, usually for an inactive phase of their life-cycles. During a recent faunistical survey of the invertebrate fauna of Bakony Mountains’ caves (Hungary) several Hymenoptera specimens were collected in hypogean environments. In this paper we report the results of the survey regarding Hymenoptera. Although the Hymenoptera material was small in numbers, they provided valuable faunistical data: very rare or rarely collected species were found, and 5 taxa are first reported from hypogean environment. Aclastus longicauda Horstmann (Ichneumonidae: Cryptinae) was found new to the Hungarian fauna, considerably extending the distributional area of this species that has been known only from Northern Europe so far. Our local results clearly indicate that, both at local and world-wide level, research focusing on the usually overlooked Hymenoptera fauna of caves will certainly provide valuable faunistical, distributional and biogeographical data.
