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How to Identify Fire Ants

Ways to Differentiate Red Imported Fire Ants from Other Ants

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The red imported fire ant is reddish brown.

The red imported fire ant is reddish brown. Its abdomen is darker than the rest of its body. Its head is about the same width as its abdomen.

USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org

Red imported fire ants defend their nests aggressively, and can sting repeatedly. Their venom causes a severe burning and itching sensation, and in rare cases, may trigger a life threatening allergic reaction. Red imported fire ants can put people and pets at risk for stings, and impact wildlife populations. If you've got fire ants, you may need to treat your property to eliminate them.

Before you rush out for some fire ant killer, though, you should be sure you've got fire ants. Ants play an important role in the ecosystem, and you don't want to kill the wrong kind.

To identify red imported fire ants, look at three things: their physical features, the ant nest, and the way the ants behave.

Differentiating Fire Ants from Other Ant Species

Look for the following traits to identify red imported fire ants:

  • Nodes. Fire ants, whether native or imported, have two nodes at the constricted "waist" between the thorax and abdomen.
  • Antennal clubs. The antennae of fire ants (genus Solenopsis) consist of 10 segments, with a two-segment club.
  • Small size. Red imported fire ant workers measure just 1.5 mm to 4 mm.
  • Size variation. Red imported fire ant workers vary in size according to caste.
  • Color. Red imported fire ants are reddish brown, and the abdomen is darker than the rest of the body
  • Standard proportion. The heads of red imported fire ants will never be wider than their abdomens in any worker caste.

It can be difficult to differentiate red imported fire ants from native fire ant species. I recommend collecting several ants from a suspected fire ant colony and taking them to your local extension office for confirmation.

Identifying Red Imported Fire Ant Nests

Fire ants live underground, in tunnels and chambers which they construct. When conditions are right for breeding, they expand their nests above ground. Looking at the construction of these mounds can help you identify red imported fire ant nests.

  • Imported fire ant mounds tend to be constructed of loose, crumbly soil. They resemble the piles left behind by digging gophers.
  • Mounds usually appear in spring or fall, or after cool, wet weather when breeding conditions are best.
  • Unlike those of native ants, red imported fire ant mounds do not have an opening in the center. The ants enter the mound from tunnels below ground level.
  • Red imported fire ant mounds usually measure up to 18" in diameter, but will often be considerably smaller.
  • Fire ants build mounds in open, sunny locations.
  • When the mound is disturbed, white brood will be visible. The larvae and pupae may look like grains of white rice in the soil.

Fire Ant Behavior

Fire ants are the hotheads of the ant world. You may be able to identify fire ants by observing their behavior.

  • Fire ants defend their nests aggressively. Any disturbance of the nest will elicit a quick response, with dozens of fire ant workers storming from the nest to do battle.
  • Fire ants will typically climb vertical surfaces when disturbed. Look for fire ant workers on tall grasses or other surfaces around the mound.

Of course, one sure fire way to find out if they're fire ants or not is to get stung (not recommended)! Fire ant venom causes an intense burning sensation. Within 24-28 days, the sting sites will form white pustules. If you've been stung by fire ants, you'll know it.

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