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Ants

Quick facts

  • Ants are 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 way to treat them.
  • The most effective way to get rid of ants is to find and treat the nest. 
  • Queens must be killed to 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 (part of the abdomen) has one or two nodes (bumps).
  • Most ants are workers and do not have wings.
  • Winged ants (queens and males) may 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 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 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

Ant castes

Typical ant castes, from left to right: queen, winged male, major worker, minor worker

Ants live in colonies and are divided into different castes: workers, males and queens. Different castes have different responsibilities in the nest.

Workers are sterile, wingless females. Some ants vary in size and are divided into major (large) and minor (small) workers. The workers take care of the work in the nest, including expanding the nest, food gathering, caring for the eggs and larvae, and defense of the nest

The reproductive members of the colony are the males and queens.

Males are generally the same size or larger than the workers. 

  • They have wings and a small head with large eyes. 
  • They are found in older, large colonies. 
  • Their sole purpose is to mate with the new queens; they die shortly afterward.

Queens are the largest members of the colony, often two to three times larger than workers. 

  • Queens have wings but break them off after mating.
  • They have very large abdomens and can live for a number of years.
  • The colonies of some ant species contain just one queen while others have multiple queens.

Mating

  • Males and queens swarm (fly) from their nest in large numbers to mate. 
  • A given species swarms during a specific time of the year.
  • After mating, the queens seek sites to begin their own nests.
  • The presence of swarming winged ants inside buildings is an indication of an indoor ant nest.

Nesting habits

Ants have a wide variety of nesting habits.

  • Some ants build nests in the soil in exposed areas, producing characteristic mounds while others nest in the soil under objects, like logs, bricks, or concrete.
  • Some species nest in homes behind moldings, baseboards, countertops, wall voids, and similar places.
  • Other ants nest in decaying or moisture-damaged wood.

Food preferences

Different ant species feed on different types of food, including starches, meats, fats, and sweets. Many ants also feed on honeydew, a sweet liquid produced by aphids and scale insects.

Food preferences can change for some species during the season depending on the requirements of the nest.

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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Reviewed in 2024

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