The invaders have consumed or outcompeted most of the native black ant population in the Southeast, threatening species like horned lizards that depend on the less aggressive black ants for food. In all, fire ants have colonized more than 310 million acres in the U.S. and Puerto Rico. Fire ants sting and kill insects as their primary food source but have been known to kill farm animals if other food is not available. Humans encountering the ants outdoors are often stung by the insects as the insects protect their territory. Imported red fire ants are the only ants that will swarm to the surface of their ant mound to attack the source of any disturbance.
Fire ants thrive in disturbed habitats, including construction sites.
Some fire ant colonies have adaptated to include more than one egg laying queen in each colony, allowing the ants to build bigger colonies. In some areas, including New Orleans, Louisiana, and San Antonio, Texas, fire ants now bite more than 50 percent of the human population each year. One study showed that 51 percent of previously unexposed medical students were stung within three weeks of arriving in San Antonio. The medical complications of fire ant stings can range from mild irritation at the sting site to death from an allergic reaction, depending on the number of stings and the physical condition of the victim. Outdoor fire ant stings have caused at least 80 deaths, according to Dr. Richard deShazo, lead author of the Annals article, director of the division of allergy and immunology and chairman of the department of medicine at the University of Mississippi Medical Center.