A new genus and species of mirine plant bug endemic to central Honshu, Japan, a region receiving the world's heaviest snowfall (Insecta: Hemiptera: Heteroptera: Miridae: Mirinae: Mirini).

A new species representing a new genus of mirine plant bug, Itoigawacoris venustulus, is diagnosed and described, based on specimens recently discovered from a geographically unique region of world's heaviest snowfall along the Fossa Magna in Niigata Prefecture, Japan. This vernal, endemic mirid was confirmed to be only associated with a Japanese boxwood, Buxus microphylla, on which the immature forms and adults were observed to co-occur before the spring thaw. Judging from the male and female genitalic structures, the present new genus is included in 'Lygus-complex' and assumed to be most closely related to Lygocoris Reuter, 1875. Some unknown microstructures found in the late immature forms of I. venustulus are also reported and discussed.