The Red Imported Fireant. Although the Red Imported Fireant is native to South America, it is best known in the United States.  Colonies were accidentally introduced into the United States in the 1930s through the seaport of Mobile, Alabama. Cargo ships from Brazil docking at Mobile unloaded goods infested with the ants.  They have since spread from Alabama to almost all of the southeastern states, as well as into California.

 Red Imported Fireants are more aggressive than most native ant species and have a painful sting. A person typically encounters them by inadvertently stepping into one of their mounds, which causes the ants to swarm up the person's legs, attacking en masse. The ants respond to pheromones that are released by the first ant to attack. The ants then swarm and immediately sting when any movement is sensed.

Red imported fire ants are extremely resilient and have adaptations to contend with both flooding and drought conditions. If the ants sense increased water levels in their nests, they will come together and form a huge ball or raft that is able to float on the water, with the workers on the outside and the queen inside. Once the ball hits a tree or other stationary object, the ants swarm onto it and wait for the water levels to recede. To contend with drought conditions, their nest structure includes a network of underground foraging tunnels and tunnels that extend down to the water table. Also, despite the fact that they do not hibernate during the winter, colonies can survive cold conditions as low as 16°F.