67 species of aquatic insects were collected from five river system of the Nobi area in Yokosuka City during the investigation from August 1985 to July 1989. These 67 species accounted for about 1/3 of species which had been recorded from the Miura Peninsula, and most of the species are found in headwaters and ponds to be preserved inthe natural environment. The five river system of Nobi area are divided into two groups; "Four river system of A to D that flow into the sea by the southern part of Nobi area" and "E river system that flows into the Hirasaku-gawa river system by the northern part of the Nobi area"; judging from the several species of Ephemeroptera and Trichoptera. The Nobi area is characterized by that many species of Odonata and Coleoptera are living in the artifical pond and that a taxonomic important hydropsychid species; Diplectroninae gen. sp., is living.