The subfamily Acaenitinae Foerster, 1869 is a small-sized group belonging to the family Ichneumonidae. It includes 250 species in 26 genera from Ethiopian, Oriental, and Palaearctic region. However, only 14 species of six genera, Arotes, Coleocentrus, Jezarotes, Phaenolobus, Spilopteron and Yamatarotes have been reported from Korea. This subfamily can be easily recognized from other ichneumonids by the combination of the following characters: subgenital plate very elongate; tarsal claws with accessory tooth. Members of Acaenitinae are parasitoids of wood-boring Coleoptera, Hymenoptera and Lepidoptera. Among them, some of parasitoids of Cerambycidae are known as intermediate carrier of Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae). In this study of the Korean Acaenitinae, we found the genus Yezoceryx from Korea for the first time, including newly recorded two species, Y. sp.1 and Y. sp.2. We provide description of the genus and two species with a key to the Korean genera of the subfamily Acaenitinae.

The subfamily Acaenitinae Föster, 1869 is a small-sized subfamily belonging to the family Ichneumonidae. Members of Acaenitinae distributes in Ethiopian, Oriental, and Palearctic Regions. Twenty six genera have been recorded in the World, and six genera are known from Korea. The biology of the Acaenitinae is not well known, however, some hosts are recorded from Cerambycidae in Coleoptera (Gardiner, 1960), Sesiidae and Tortricidae in Lepidoptera (Ulbricht, 1909; Starke, 1956). Generally female is easily distinguished from that of other subfamily of Ichneumonidae. They can be recognized by their very elongate subgenital plate, and by the auxiliary tooth on the tarsal claws. Male can be also easily recognized by the form of the claws and the facial shape. In this study, we found a newly recorded genus Yezoceryx, belonging to the Tribe Acaenitini, with two species in Korean fauna. Illustrated key of species and genera, diagnosis and photographs of each species are provieded.