There are several species of fire ants in the United States. They get their common name from the painful, – and sometimes fatal – sting that the workers deliver when they are disturbed.
In a colony of fire ants, workers can range in size from less than 1/8″ to more then ¼”. Scientists use the word polymorphic to describe this variation in worker size.
Fire ants, like all other ants, have a three-segmented body. The fire ant's first two segments are reddish in color. The third segment is often dark colored, almost black.
The first segment of the fire ant's body is the head. The large workers of the tropical fire ant, Solenopsis geminata (Fabricius), have heads that are shaped differently from the heads of the small workers.
Fire ants have eyes, but since they live underground, they receive a lot of sensory information through their antennae. Scientists use the size of the antennae to help distinguish one type of ant from another.
Scientists study the jaws, or mandibles of fire ants to help identify the species. Most species of fire ants have something different about the mandibles. The red imported fire ant, Solenopsis invicta (Buren), has four teeth on its mandibles. The southern fire ant, Solenopsis xyloni (McCook), has three teeth. (This ant is also known as the California fire ant.) The tropical fire ant, Solenopsis geminata (Fabricius), has smooth mandibles with no teeth.
The middle section of the fire ant's body is called the thorax. All three pair of legs are attached to the thorax. In the summer, the fire ant colonies produce winged fire ants. Their wings are also attached to their thorax. The thorax is the segment of the body that provides movement for the ant.
The third segment is called the abdomen. The beginning of the abdomen has several small segments that give the ant the “pinched” waist. The number of small segments helps scientists identify an ant specimen. The large part of the abdomen is called the gaster. This is where the organs of the body and the stinger are located.
The fire ant stinger is different from the stinger of a honeybee. The fire ant stinger has no barb, so the ant can sting over and over. The fire ant venom is very strong and some people are very allergic to it. A few people go into shock after being stung and fire ants cause a few fatalities each year.
Scientists often have to use magnifying glasses or microscopes to study the bodies of fire ants. The various parts are very small and hard to see. Since fire ants sting and bite, most people prefer not to get very close to them. Most people identify fire ants by the mounds of soil that they build and the aggressive way they defend their colony. These are things that can be observed from a safe distance.