Distribution of Ecnomus McLachlan, 1864 (Trichoptera, Ecnomidae) from the Lower Mekong River with a description of Ecnomusstungtrengensis new species

BACKGROUND: Trichoptera were surveyed from four different physiographic regions of the Lower Mekong River, including the Northern Highlands, the Khorat Plateau, the Tonle Sap Basin and the Mekong Delta in Myanmar, Laos, Thailand, Cambodia and Vietnam. NEW INFORMATION: Twenty-three species of the genus Ecnomus, including a new species, were identified and mapped. Ecnomusmammus Malicky & Chantaramongkol, 1993 is a common species which is found from Tonle Sab Basin and Mekong Delta. Ecnomusalkmene Malicky & Chantaramongkol, 1997, E.volovicus Malicky & Chantaramongkol, 1993 and Ecnomusquordaio Malicky, 1993 are the common species in the area of the Northern Highlands and the Khorat Plateau. Ecnomusplotin Malicky & Laudee 2010 is found in the Mekong Delta. Ecnomustriangularis Sun, 1997 is a new species record for Southeast Asia. In addition, E.stungtrengensis sp. n. is described and illustrated. The male genitalia of E.stungtrengensis sp. n. are clearly different from those of other species in the genus Ecnomus by the shape of superior appendages which are slender and bent downwards distally in lateral view.