This is one of large water beetles in the family Dytiscidae, order Coleoptera. The adults are 28 to 33 mm long with green or blackish-brown backs. They are distributed in the plains and hilly areas of northern Noto. They live in clean water, including muddy wetlands and irrigation ponds into which spring or stream water flows. However, because of the development of ponds and marshes, the improvement of agricultural land, the increase in abandoned farmland and the invasion of alien species, the population has decreased. After they were last seen on the Noto Peninsula in 1960, it was believed that they had gone extinct. However, in 1984, they were seen again in Chiba Prefecture. The Environment Ministry’s Red List classifies Sharp gengoromodoki as a Threatened Species Class I. Under the “Ordinance for the Protection and Enhancement of Hometown Ishikawa”, in 2005, the prefectural government designated it as a rare species that seriously needs to be protected.