I like to think of myself as a fairly even-keeled person. I have a short list of hated things: root canals, traffic, wood rot, and the like. In the natural world, the list is even shorter, but it’s topped by a large margin by fire ants, who were, in my opinion, designed to inflict misery and pain. I’ve yet to meet someone who takes a strong counterpoint to this position, so if I’ve missed the boat, please let me know.
Explore This IssueACEP Now: Vol 40 – No 06 – June 2021
Names include fire ants, Solenopsis invicta, red ants, and red imported fire ants (RIFAs). There are also black imported fire ants (BIFAs). The difference between the two (red and black fire ants) is largely academic, as they have similar biologies and behaviors. There are also hybrids of these two species.
Distinct attributes of the fire ant include a narrow wasp-like waist, or pedicel, that is composed of two segments (see white arrow). Workers vary in lengths between 1/8 and 1/4 inches. They have large biting mandibles with four teeth, and their antennae have 10 segments, ending in a two-segmented club. A sting is present at the tip of the rear segment (gaster). The body color is usually red to brown.
History and Distribution
Fire ants first entered the United States somewhere around 1918 in Alabama—brought north from South America in dumped ballast from ships. They immediately began to spread though the costal Southeast and now infest most of that region of the United States.
Northern migration of fire ants was thought to be limited by the colder climate because winter temperatures freeze the soil deeply enough to affect overwintering colonies. However, recent research shows RIFA colonization in colder higher elevations.
Mounds: Fire ant mounds look like heaped-up fluffy dirt. The mounds do not have central entrance holes on the surface, which distinguishes them from other ant hills. The mounds have interconnecting galleries and underground tunnels that can extend to the surface five to 25 feet away from the mound.
Colony life: Fire ants are social insects that nest in the soil in large colonies that contain 200,000 to 400,000 workers, although some super colonies have millions of individuals.
Fire ants spread by saltatory swarming. Reproductive male and female ants leave the mound en masse, fly into the air, and mate while airborne. The fire ant queens fall back to the ground, shed their wings, and start new colonies where they land.
Most of the ants in the colony are infertile female workers gathering food and caring for the colony—and all can sting. They are omnivores and feed on almost anything—invertebrates and vertebrates as well as plants and honeydew. There is usually one queen per colony, but some colonies have several that all lay eggs.
Attitude: These ants are highly aggressive. They scavenge food for the colony and vigorously attack intruders to defend their mound. They do so by swarming in large numbers to attack any animal disturbing their nest. They instinctively climb vertical surfaces, including limbs. Although they are small, their sting and strength in numbers allow them to overwhelm and kill much larger prey.
Fire ants use their strong jaws to dig in and pinch human skin. This bite anchors the insect to the skin and acts as a pivot, allowing it to inject venom multiple times using its sharp stinger. A single ant stings an average of three times before removal.