Revision of Palearctic Trissolcus Ashmead (Hymenoptera, Scelionidae)

Species of Trissolcus Ashmead are potent natural enemies of stink bugs (Pentatomidae). Research on biological agents to control the brown marmorated stink bug, Halyomorpha halys (Stål) (BMSB), in Western Europe requires reliable taxonomic resources for identification of Trissolcus wasps. To aid this research endeavor, we present a species identification key to females of Palearctic Trissolcus. Morphological characters and concepts of the genus and species groups are discussed. We discovered a number of nomenclatural and identification issues that we here rectify.