On the specimens of Dytiscoidea deposited in the Osaka Museum of Natural History, with special reference to the endangered and rare species (Insecta: Coleoptera)

The specimens of Dytiscoidea deposited in the Osaka Museum of Natural History were investigated. Reports are made on the specimens of the endangered and rare species, mainly collected from Kinki District (Japan). The specimens throughout the 1920s to the 60s from Osaka and Hyogo Prefectures reveal the environmental situations before the rapid process of urbanization and pollution of habitat took place.