How a port became a foothold
Red imported fire ants are native to South America. They established themselves near Mobile, Alabama, in the 1930s, probably arriving in soil carried by ships. The precise journey is uncertain, but a small number of founding colonies was enough: each colony could produce winged queens and males that mate in the air and start new nests.
Two routes of expansion
Once established, ants spread on their own through mating flights and by moving colonies into nearby ground. People unintentionally carried them farther when infested soil, sod, or nursery plants were transported to new sites. That combination—slow local expansion and sudden jumps between distant places—helped the ants spread across the warm South.
Their colonies also withstand conditions that can wipe out other insects. During floods, workers can cling together in floating rafts, keeping queens and young above water until the colony reaches dry ground. A mound may look like a single nest, but it shelters a large, organized colony beneath the surface.
A nuisance built into daily life
When a nest is disturbed, workers swarm out and sting repeatedly. Their venom causes a burning, itchy welt and can trigger a severe allergic reaction in some people. Mounds also interfere with mowing and farming, while colonies prey on small animals and compete with native species.
The lasting regional problem came from more than the ants’ painful sting: colonies could multiply, survive local hazards, and hitch rides with human commerce. A patch of soil moved for landscaping could carry an invasion well beyond the nearest mound.
