Scientists distinguish fire ants from other ants by examining the ants and comparing parts of their bodies. The first thing the scientists look at is the ant's narrow “waist”. All ants have segments in this area. Some ants have one segment in their “waist” while other ants have two segments. Fire ants belong to the group that has two segments in their “waist”.
The next characteristic that scientists look at is the shape of the antennae. Fire ant antennae have ten segments. Their antennae end in a club shape that is made of two segments.
To distinguish the various species of fire ants, scientists look at the number of teeth on their mandibles. The red imported fire ant, Solenopsis invicta (Buren), has four teeth on its mandibles. The southern fire ant, S. xyloni (McCook), has three teeth on its mandibles. (Many people call this ant the California fire ant.) The tropical fire ant, S. geminata (Fabricius) has no teeth on its mandibles.
Most homeowners do not have a magnifying glass or a microscope for identifying ants. Since fire ants bite and sting very aggressively, very few homeowners want to risk getting a close look at the ants. Many people prefer to identify fire ants by the way they behave.
Fire ants nest in the ground. They prefer open, sunny areas. The fire ant workers build a mound of soil on top of the nest. The mound is often beside concrete sidewalks, driveways, or the foundations of homes. Fire ants also nest in electrical boxes and transformers. The mounds can be as high as 18″.
Fire ants are VERY aggressive, especially when the mound is disturbed. Hundreds of ants rush out to confront the intruder. The defenders run up onto the legs and they all bite at once. At the same time, hundreds of workers can be seen scurrying to safety carrying eggs and immature ants.
In a colony of fire ants, there are workers of different sizes. The very small workers can be less than 1/8″ long. The very large workers can be more than ¼” long. If someone disturbs the mound, he or she could see workers of every size. It will not be safe to stay and observe them, because after they bite, the workers begin to sting. The sting is very painful and some people experience an allergic reaction. Most people develop a small blister at the site of the sting.