Rhopalosomatidae are an unusual family of wasps (Hymenoptera: Aculeata)comprising less than 100 species found in the tropics and subtropics ofall continents except Europe and Antarctica. Whereas some species resemblenocturnal Ichneumonidae, others might be mistaken for spider wasps ordifferent groups of brachypterous Hymenoptera. Despite their variedmorphology, all members of the family supposedly develop as larvalectoparasitoids of crickets (Orthoptera: Grylloidea). Here, we report on thefirst record of a fossil rhopalosomatid larva which was discovered inmid-Cretaceous amber from northern Myanmar (Burma). The larva is attached tothe lateral side of a cricket between the metafemur and the abdomen,impacting the natural position of the hind leg, exactly as documented formodern species. Additionally, the larval gestalt is strikingly similar tothose of extant forms. These observations imply that this behavioralspecialization, e.g., host association and positioning on host, likelyevolved in the stem of the family at least 100 million years ago.