Identifying and Controlling Pavement Ants

Tiny pavement ants eating honey

fractality23 / Flickr / CC BY 2.0

Several different types of ants are commonly seen around the home. Of the more than 22,000 different species, only a fairly small fraction poses problems for homeowners. These common species range from fairly large and destructive carpenter ants (Camponotus spp.) to the small and relatively harmless pavement ants (Tetramorium caespitum), which are little more than a nuisance.

Pavement Ant Identification

The pavement ant is a small specimen, 1/10 to 1/6 inch long. It is brownish-black with pale-colored legs. With a magnifying glass or microscope, you can see that it has two spines between its body parts and tiny stiff hairs covering its body. During spring and early summer, you may see pavement ants with wings.

These are the ants you frequently see colonizing out of the cracks in sidewalks, but it's not uncommon to also see them crawling across the kitchen floor in search of a crumb, trailing across your picnic blanket, or following the smell of BBQ on your patio. The pavement ant is one of the most common species in the U.S., found in all 50 states. 

Behavior

When a pavement ant colony is outdoors, it can be easily identified by the small cone-shaped mound of soil that usually sits atop the nest. This ant often builds its colony beneath concrete cracks in driveways and sidewalks, and beneath rocks and logs. It tunnels into the soil to dig out space for its colony, pushing the dirt up through the top of its nest, creating the trademark sandhill-like mounds.

A typical colony will have 3,000 to 5,000 ants, although there can be as many as 30,000 ants in a single colony. There can be more than one queen in each colony, and since it is the queen that produces all the offspring, there can be a lot of baby ants in one pavement colony.

Although you may see pavement ants during the day, they are most active at night. If you happen to have more than one colony on your property or another one nearby in the neighborhood—and you happen to be observing at the right time—you just might witness the unique event of an ant battle or its aftermath. Pavement ant colonies will fight for territory, and these battles can leave hundreds of dead ants on the battlefield.

Ants vs. Termites

In the spring and early summer, swarms of winged pavement ants will fly to mate and reproduce. These winged ants can be confused with termites because termites also swarm at this time of the year. But ants can be distinguished from termites by several characteristics:

  • Wings: The pavement ant's front wings are longer than its back wings; termite wings are of equal length.
  • Body: Ants have a narrow waist; the termite's thick waist makes it look like it has only one body part.
  • Antennae: Ants' antennae are elbowed; termites' are straight.
  • Size: The pavement ant is much smaller than the termite.

Colonies in the Home

Because of their small size, pavement ants can easily get into homes and buildings through tiny cracks, around doors and windows, and beneath spaces under the siding. One of their most common entry points is beneath sliding doors.

The ants will also nest inside houses, setting up their colonies within walls or under flooring and in woodwork, masonry, or insulation. Although pavement ants do not destroy wood or other building materials, they can be a definite nuisance when large numbers infiltrate a home. These colonies can be much more difficult to locate and eliminate than those that are built outdoors. Like other species of ants, Tetramorium caespitum may enter homes in large numbers in search of food. They will eat almost anything that humans eat, and some things we don't, such as live and dead insects. But their real preference is for meats and grease. Keeping food sources sealed and kitchens spotlessly clean is one of the best ways to discourage ant infestations.

The pavement ant is rarely aggressive, but it can bite and sting when disturbed. Though it's bite is generally too weak to penetrate human skin, it can cause allergic reaction or rash in people who are sensitive to the bite.

Controlling Pavement Ants

Spraying pavement ants directly is rarely very effective, because this kills only the workers you can see; more will quickly be sent out from the colony to forage. Whether the colony is outdoors or hidden somewhere in your house, baiting the ants is a much more effective strategy. Placing bait stations along the observed trail where you see ants traveling will cause the workers to find the bait and carry it back to the nest, where the queen (or queens) will feed on it. This will soon eliminate both the queens and future populations. Any number of effective chemical ant baits are available, but a safe homemade ant bait can be made by mixing household borax with honey or syrup.

Of the commercial ant baits, those containing methoprene and pyriproxyfen are regarded as relatively safe and low in toxicity in comparison to other chemicals, such as hydramethylnon, various neonicotinoids, avermectin, fipronil, metaflumizone, and fenoxycarb, some of which are considered probable carcinogens.

If you do happen to trace the ant trail back to an outdoor, below-ground nest, drenching the nest with an approved insecticide spray can also be effective at eliminating the population.