In this case, "fire ants" refers to two species of fire ants in the genus Solenopsis: the red imported fire ant, Solenopsis invicta Buren, and the black imported fire ant, Solenopsis richteri Forel. They were introduced accidentally into the United States and are therefore referred to as "imported fire ants." The two species do not occur in the same geographic location in South America. In the United States, they have interbred, resulting in sexually active hybrids.
Red imported fire ants: S. invicta was described in 1972 by Buren. Before then, other scientific names used for this species included Solenopsis wagneri Santschi, described in 1916, or Solenopsis saevissima var. wagneri Santschi. Although the use of S. wagneri preceded S. invicta, the latter is used today. This species was accidentally introduced to the United States through the port at Mobile, Alabama, in about 1933.
Black imported fire ants: S. richteri was also accidentally introduced through the port of Mobile, Alabama, in 1918. Until 1972, S. richteri was not recognized as a different species from the red imported fire ant. Today, the black imported fire ant has a limited range.
Imported fire ants can cause serious medical, economic, aesthetic, and ecologic problems.
Find more information about fire ants in eXtension's Imported Fire Ant Resource Area.