Carpenter Ant Facts: Identification, Behavior & Damage

Key Points

• Carpenter ants are among the largest ants in the United States, ranging from 3.4–13 mm long.

• Unlike termites, they don’t eat wood—they excavate it to create tunnels and nesting chambers.

• Moist or decaying wood is their preferred nesting site, often linked to leaks or humidity.

• Colonies can reach 3,000 to 100,000 ants, with queens living up to 25 years.

• Early detection and moisture control are critical to prevent serious structural damage.

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What Do Carpenter Ants Look Like?

Carpenter ants are large, strong ants that can vary in color depending on the species. Most are black, though some appear red, brown, or even two-toned with black and red bodies. They measure 3.4 to 13 mm in length, with the queen reaching up to 20 mm.
Their most distinctive features include:

• Large mandibles used to chew and tunnel through wood.

• A narrow waist and bent antennae, differentiating them from termites.

• Winged swarmers (reproductive ants) that appear during spring or early summer.

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Carpenter Ant Anatomy

• Head: Prominent with powerful mandibles for excavation.

• Thorax: Rounded and smooth, unlike termites whose thorax and abdomen blend together.

• Color: Typically black, but some species are red, brown, or a mix of both.

• Size Range: Workers (3.4–13 mm), winged males (up to 18 mm), queens (up to 20 mm).

• Lifespan: Workers live several months; queens can survive for decades.

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Behavior & Colony Structure

Carpenter ant colonies are highly organized and divided into castes:

• Queen – Sole egg-layer, capable of living up to 25 years.

• Workers – Tunnel into wood, care for larvae, and gather food.

• Soldiers – Larger workers responsible for defending the colony.

A typical mature colony houses about 3,000 adult ants, though larger colonies can exceed 100,000 individuals.
Carpenter ants form two types of nests:

1. Parent colonies – Contain the queen, eggs, and workers.

2. Satellite colonies – Contain workers, pupae, and larvae that expand from the main nest.

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Carpenter Ant Nests

Carpenter ants prefer moist, decaying, or water-damaged wood for nesting. Common locations include:

• Window sills, door frames, and roof eaves

• Wooden beams or wall voids near plumbing leaks

• Trees or stumps with internal decay

Outdoors, they build nests in rotting logs, tree hollows, or under bark. Indoors, they take advantage of wood weakened by moisture, often near bathrooms, kitchens, and attics.

Because they remove wood to make galleries rather than consume it, you’ll often find small piles of sawdust-like shavings beneath woodwork or baseboards—an early warning sign of an infestation.

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Life Cycle of Carpenter Ants

Carpenter ants undergo complete metamorphosis:

Their life cycle begins with a nuptial flight in spring or early summer, when winged males and females mate. Afterward, the males die, and fertilized females remove their wings and start new colonies.
A colony can take 3–6 years to fully mature. Growth slows significantly in cold weather, which can delay development by up to ten months.

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What Do Carpenter Ants Eat?

Although they tunnel through wood, carpenter ants do not eat it. Instead, they feed on a variety of foods such as:

• Sweet substances like honeydew, fruit juices, and household sweets

• Proteins such as meats and other insects

• Greasy foods or pet food left uncovered

Outdoors, they hunt insects and honeydew from aphids. Indoors, they scavenge for sugary or fatty items, often at night.

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Damage Caused by Carpenter Ants

While carpenter ants don’t consume wood, the damage from their excavation can weaken structural integrity over time. Their tunnels create a polished, sanded appearance inside damaged wood.
Signs of carpenter ant damage include:

• Small piles of wood shavings resembling pencil shavings

• Rustling sounds within walls or woodwork

• Winged ants emerging from walls or ceilings

• Hollow-sounding wood when tapped

Unchecked colonies can expand into multiple satellite nests, leading to widespread damage that mimics termite activity.

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Carpenter Ant vs. Termite Infestation

It’s easy to confuse carpenter ants with termites, but several traits help differentiate them:

While termites eat wood, carpenter ants only remove it to build their nests—so their damage is typically slower but still significant over time.

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How to Prevent Carpenter Ants

• Repair leaks and eliminate sources of moisture.

• Trim trees and shrubs touching your home’s roof or siding.

• Seal entry points around utility lines, windows, and foundation cracks.

• Store firewood away from the home and off the ground.

• Inspect annually, especially after heavy rains or roof leaks.