The Nature Conservancy in North Carolina

Fire Ant - (Solenopsis invicta Buren)

The red imported fire ant is on the worst pest list for the Sandhills.

Adult red imported fire ants are reddish to dark brown and occur in five forms: (1) minor workers, about ¹/8 inch long; (2) major workers, about ¹/4 inch long; (3) winged males and (4) females, each about ¹/3 inch long; and (5) queens, about ¹/3 inch long.

Fire ant mounds vary in size, usually in direct proportion to the size of the colony. For example, a mound that is 2 feet in diameter and 18 inches high may contain about 100,000 workers, several hundred winged adults, and one queen. In addition, when the mound of an active fire ant colony is broken open, whitish rice grain-like larvae and pupae usually can be found. These immature ants will eventually develop into workers or winged adults. Mounds constructed in clay soils are usually symmetrical and dome-shaped; mounds built in sandy soils tend to be irregularly shaped. It is often difficult to distinguish the red imported fire ant from the tropical fire ant and the southern fire ant, which are also found in North Carolina.

During the spring and summer, winged males and females leave the mound and mate in the air. After mating, females become queens and may fly as far as 10 miles from the parent colony. However, most queens descend to the ground within much shorter distances. Only a very small percentage of queens survive after landing. Most queens are killed by foraging ants, especially other fire ants. If a queen survives, she sheds her wings, burrows into the ground, and lays eggs to begin a new colony. In the late fall, many small colonies of fire ants will appear. Many of the colonies will not survive the winter unless the weather is mild.

To find food, workers forage around their mound. These ants usually travel in underground tunnels that radiate from the mound. If the mound is disturbed, ants swarm out and sting the intruder.