These ants are native to Argentina, and the red imported fire ant most likely came from here when they first invaded the United States; in particular, populations of these ants have been found in the provinces of Chaco, Corrientes, Formosa, Santiago del Estero, Santa Fe, and Tucumán. The northeastern regions of Argentina are the most credible guess where the invading ants originate. In Brazil, they are found in northern Mato Grosso and in Rondônia and in São Paulo state. The red imported fire ant and "S. saevissima" are parapatric in Brazil, with contact zones known in Mato Grosso do Sul, Paraná state and São Paulo. In Paraguay they are found throughout the country, and have been recorded in Boquerón, Caaguazú, Canindeyú, Central, Guairá, Ñeembucú, Paraguarí, and Presidente Hayes departments; Trager claims that the ant is distributed in all regions of the country. They are also found in a large portion of northeastern Bolivia and, to a lesser extent, in northwestern Uruguay.