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Ants

Quick facts

  • Ants are very common pests found in and around homes.
  • The first step in control is to identify the ants - knowing the species is necessary to understand where they may be nesting, their food preferences and the best method of treatment.
  • The most effective way to get rid of ants is to find and treat the nest. 
  • Queens must be killed to properly eliminate a colony.

Identifying ants

Ant identification can be challenging. Correct identification is important as food preferences, nesting sites, and other habits differ. These factors influence the most effective methods for controlling them. If you have an ant you cannot identify, talk to an expert who can.

Important characteristics

Ants are recognized by the following:

  • A pair of elbowed (bent) antennae on the head. 
  • A constricted (pinched) area between the thorax and abdomen called the petiole. The petiole (actually part of the abdomen) has either one or two nodes (bumps).
  • Most ants are workers and do not have wings.
  • Winged ants (queens and males) may occasionally be seen when they swarm.

Most ants are brownish to black. They can also be yellow, reddish, or black and red. Color can be helpful but is not always definitive for identifying ants.

Worker ants vary in size from as small as 1/20 inch long up to 1/2 inch long. Size can help narrow down which ant is present but it is usually not enough to identify it without looking at other characteristics.

These characteristics are important to help identify different species of ants, although they may not be easy to see:

  • The number of nodes in the petiole and whether they are clearly visible or are hidden.
  • The shape of the thorax.
  • The presence or absence of spines on the back of the thorax.
  • The number of segments in the antennae and whether a club (enlarged segment at the tip) is present.
  • The presence or absence of simple eyes (ocelli) on the head.

An ant’s biology can also help identify them, such as where they are nesting and when they swarm (when females and males fly out of their nest).

How to tell an ant from a termite

Winged termite
Winged ant

Ants are sometimes mistaken for winged termites called swarmers.

Ants are different from termites by having a narrow, constricted waist, bent antennae and hind wings shorter than front wings.

Termites have a more rectangular-shaped body with no constrictions; straight, beaded antennae; and four wings of equal size and shape that are much longer than the body. Termite wings fall off very easily and are usually found near where they emerge.

Ants are commonly seen in the open, as are winged termites when they swarm. But termite workers, which are creamy-white and wingless, avoid light and are rarely seen unless disturbed.

Biology of ants

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Damage caused by ants

Damage from ants varies. Most are primarily a nuisance, causing little actual damage, although they can be annoying and even upsetting when found in your home.

Some species can infest food. Others, like carpenter ants, can weaken wood in structures. While not common, at least one species, Pharaoh ant, has been known to transmit some diseases, like Salmonella.

Some ants nest in lawns. Fortunately, they do not feed on or injure grass but their presence can be annoying. Cornfield ants nest in lawns where the grass is thinning or has become bare, creating small mounds. Field ants can nest in areas of the lawn that are growing well, creating mounds up to a foot in size. These large, high mounds can interfere with lawnmowers.

How to control ants

The first step in ant control is to identify them. Knowing which ant is present tells you where they like to nest and what they like to eat. Knowing this helps with the best way to control them.

The most effective way to control ants is to put insecticide into the nest and kill the queen(s). This may be done with a direct treatment or by using bait. Killing foraging workers has little effect as just a small percentage of ants are out of the nest at any given time.

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Identifying ants with one node

Open a drawer for more specific information and photos of each type of ant listed. It is often challenging to recognize ants from a picture. Because different species may be treated differently, be sure an ant problem is correctly identified before attempting control.

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Identifying ants with two nodes

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Jeffrey Hahn, Extension entomologist and Patrick Liesch, University of Wisconsin-Extension

Reviewed in 2020

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