History of the Fireant

More than 65 years ago, the red imported fire ant, Solenopsis invicta Buren, was accidentally brought into Mobile, Alaba

ma from South America. It now infests more than 275 million acres comprising most of nine southeastern states and Puerto Rico with small infestations in Tennessee, Oklahoma, New Mexico and California. Another species, the black imported fire ant, Solenopsis richteri Forel, was also introduced, but the range of this species remains limited to northeastern Mississippi, northwestern Alabama and southern Tennessee. A large population of hybrid fire ants (S. richteri x S. invicta) exist in a band between the two parent species and can be found in southeastern Tennessee, northwestern Georgia, South Carolina, North Carolina, northern Alabama, and northern Mississippi. Fire ants can travel long distances when newly-mated queens land on cars, trucks or trains or when winged forms are carried by the wind. Shipments of nursery stock or soil from an infested area may relocate entire colonies or nests.

Fire ants are social insects and unlike many insect pests, they are very organized. Red imported fire ant colonies consist of the brood and several types (castes) of adults. The whitish objects often found at the tops of the mounds are actually the ant’s developmental stages—the eggs, larvae and pupae. Types of adults are:

The winged forms, or reproductives, live in the mound until their mating flight, which usually occurs in the late morning and afternoon soon after a rainy period. Mating flights are most common in spring and fall. Males die soon after mating, while the fertilized queen lands and walks around to find a suitable nesting site, sheds her wings, and begins digging a chamber in which to start a new colony. Sometimes, several queens can be found within a single nesting site.

A newly-mated queen lays about a dozen eggs. When they hatch 7 to 10 days later, the larvae are fed by the queen. These larvae will develop into small worker ants that will feed the queen and her subsequent offspring. Later on, a queen fed by worker ants can lay from 800 to 1,000 eggs per day if needed. Larvae develop in 6 to 10 days and then pupate. Adults emerge 9 to 15 days later. The average colony contains 100,000 to245,000 workers and up to several hundred winged forms and queens. Queen ants can live 7 years or more, while worker ants generally live about 5 weeks, although large workers can survive much longer.

In addition to hybrid imported fire ants, there are two kinds of red imported fire ant colonies—the single queen and multiple queen forms. Workers in single queen colonies are territorial. Workers from multiple queen colonies move freely from one mound to another, which has resulted in a dramatic increase in the number of mounds per acre. Areas infested with single queen colonies contain 40 to 150 mounds per acre (rarely more than 7 million ants per acre). In areas with multiple queen colonies, there may be 200 or more mounds and 40 million ants per acre.