<i>Araucnephia</i> Wygodzinsky & Coscarón is a Neotropical black fly genus in which only one species from Central Chile is known. Another species has now been found in Corrientes province on the eastern side of the. Iberá tropical swamps of Argentina, on the western border of the mountainous region of southern Brazil. This new species, <i>A. iberaensis</i>, is herein described and illustrated and information on its bionomics is recorded. It is an interesting species because previous to its discovery no black fly genus or subgenus from Central Chile region has been found in tropical areas, because these two regions are separated by the Monte and Pampas realms. Similarly, no Brazilian genus or subgenus has crossed the Andes mountains to Chile. A comparison with other Neotropical, Nearctic, Ethiopian (Afrotropical) and Australian Prosimuliini (sensu Crosskey & Howard) showed <i>Araucnephia</i> to be a valid taxon most closely related to <i>Araucnephioides</i> (sympatric in Chile). <i>Araucnephia</i> also shows great affinities with <i>Lutzsimulium</i> from Southeast Brazil and Argentina and Paracnephia from South Africa.Facultad de Ciencias Naturales y Museo