Both the genus Mesocoelus and the species M. philippinensis Muesebeck have hitherto been unrecorded from Japan. The junior author reared four specimens of this very rare and remarkable species from the larvae of Acrocercops transecta Meyrick (Gracilariidae), a leaf miner of Lyonia elliptica Okuyama, on June 17th, 1955, at Hikosan. Kyushu, Japan. The species was kindly determined by Mr. Muesebeck while the senior author was in the U. S. National Museum in 1956. The occurrence of this genus and species in Japanis of special interest from the zoogeographical point of view.
free text keywords: ワタナベコマユバチ, Mesocoelus philippinensis Muesebeck, コマユバチ科