In recent surveys of black flies in Arunachal Pradesh, North-East India, five species are newly recorded from Arunachal Pradesh: Simulium (Montisimulium) nemorivagum Datta, 1973, Simulium (Gomphostilbia) darjeelingense Datta, 1973, Simulium (Gomphostilbia) decuplum Takaoka & Davies, 1995, Simulium (Simulium) barnesi Takaoka & Suzuki, 1984 and Simulium (Simulium) pradyai Takaoka & Somboon, 2008, of which the latter three species also represent new records from India. Taxonomic reviews of two species of black flies reported from Assam show that Simulium (Gomphostilbia) unum Datta, 1975 is a junior synonym of Simulium (Gomphostilbia) darjeelingense, and the larva of Simulium (Gomphostilbia) sp. nr. varicorne Edwards is identifiable as Simulium (Gomphostilbia) parahiyangum Takaoka & Sigit, 1992.