Fire ants are indigenous to the U.S. However, the accidental introduction of Solenopsis invicta (red imported fire ant) into Mobile, Alabama on a cargo ship during the 1930s, the introduction of Black imported fire ants, and now a hybrid species of fire ants has changed the playing field in terms of control. The imported species and hybrid ants are still a research work-in-progress.
In all, fire ants infest hundreds of millions of acres, and the United States Department of Agriculture's (USDA) projected infestation map predicts that red imported fire ants will eventually be coast-to-coast right across the south. The USDA introduced a quarantine program for imported fire ants in the 1950s.
Fire ants can travel long distances when mated queens land on cars, trains, trucks, or are even carried on the wind. The aggressive ants, whose collective stings can be fatal, are causing major disruption to farming activities from workers in the fields to vulnerable livestock with infestations making some pastures effectively unusable.