Carpenter ants

What carpenter ants look like

Carpenter ants are the largest ants found in Ontario homes. Workers range from about 0.76 to 2.54 cm, and a single colony produces workers of noticeably different sizes, which is a useful identifier on its own. Most are black, though some are reddish brown or a mix of red and black. The body has a smooth, evenly rounded thorax when viewed from the side, a single node at the waist, and elbowed antennae. Winged reproductives appear in spring and early summer and are often mistaken for termites, but an ant has a pinched waist, bent antennae and front wings longer than the back wings. Carpenter ants are mostly active at night, so a few large ants crossing a kitchen floor after dark tells you more than daytime sightings do.

Signs you have carpenter ants

• Coarse frass. Small piles of material that looks like pencil shavings mixed with insect parts, below window frames, baseboards, sill plates or deck framing.
• Large ants indoors in winter. Big black ants walking inside during cold months, which points to a nest inside the structure rather than outdoors.
• Rustling in walls. A faint dry crackling from a wall or ceiling void at night, which is the sound of the colony working.
• Winged swarmers. Flying ants at windows and light fixtures in spring, usually the sign of a mature colony that has been there for years.
• Hollow, smooth galleries. Wood that sounds hollow when tapped and reveals clean, sanded looking tunnels when opened.
• Night trails. Lines of ants after dark along foundation walls, deck rails, utility lines, tree limbs or fence tops leading to the house.

Frass with a moisture problem nearby is the combination worth acting on quickly.

Why carpenter ants turn up around Ottawa and Toronto properties

Moisture is the underlying cause, every time. Carpenter ants prefer wood that is damp, softened or already decaying, because it is easier to excavate. Ontario weather supplies plenty of opportunity: freeze and thaw cycles, ice damming on Ottawa rooftops, heavy spring rain across the Toronto GTA, and humid summers around Hamilton harbour. The specific problem spots are predictable. Leaking roof flashing and valleys, blocked gutters and downspouts discharging at the foundation, poorly sealed window and door frames, bathroom and kitchen leaks, damp basements and crawl spaces, sill plates behind failed caulking, and deck ledger boards holding water. Outside, the colony often starts in a stump, a dead tree limb, a woodpile against the wall or landscape timbers, then sends satellite nests indoors. Overhanging branches and stacked firewood give them a bridge straight to the building.

Are carpenter ants dangerous?

The health risk is low. Carpenter ants do not transmit disease and they do not sting in the way a wasp does, though a large worker can deliver a sharp pinch with its jaws and may spray formic acid into the bite, which stings briefly. They can walk across food surfaces, so basic kitchen hygiene still applies. The property risk is the real issue. Carpenter ants excavate wood to nest in it. They do not eat it, which is an important distinction, and they push the chewed material out as frass rather than digesting it. Over years, a mature colony with satellite nests can hollow out sill plates, joists, studs, window frames and deck structure, and the galleries follow exactly the wood that is already damp and weak. The damage is slow but it compounds, and it is frequently found only when a renovation opens a wall.

How to keep carpenter ants away

• Fix the moisture first. Repair roof and plumbing leaks, clear gutters, extend downspouts well away from the foundation and improve grading that slopes toward the house.
• Replace wood that is already soft or rotten around window sills, door frames, sill plates, deck ledgers and basement framing.
• Move firewood, lumber and landscape timbers off the ground and well away from the walls, and never store firewood indoors for long.
• Cut back tree limbs and shrubs touching the roof, siding or utility lines so ants have no bridge to the structure.
• Seal cracks and gaps at the foundation, around pipe and cable entries, window frames and where siding meets the sill.
• Ventilate basements, crawl spaces and bathrooms, and run a dehumidifier where the air stays damp through the summer.

Treat the damp wood as the real problem and the ants have far less to work with.

How GO! Pest Control handles carpenter ants

• Inspection. We trace the trails, sound the suspect timbers, locate the parent and satellite nests and identify the moisture source that is feeding the problem.
• Treatment. We treat the nests and the trails directly, using baits the workers carry back to the colony together with targeted applications where the galleries are.
• Repairs advice. We show you the wet wood, the failed flashing, the downspout or the grading that needs fixing, because treatment alone does not solve a moisture problem.
• Follow-up. We return to confirm the activity has stopped, check for satellite nests we have not yet seen and re-treat where trails reappear.
• Advice. We go over storage, landscaping and ventilation habits that keep the structure dry and unattractive to the next colony.

We are licensed, insured and bonded, and we work in homes, apartments, condos and businesses across the Toronto GTA, Ottawa and Hamilton.

Common questions about carpenter ants