Identification
The carpenter ant can be recognized by its large size, its black or black and red body, its thorax evenly rounded when viewed from the side and its petiole with a single node. It does not eat wood: it excavates smooth galleries in it to house its colony. Over time, these galleries can weaken structural wood in severe cases.
A parent colony and satellite nests
A parent colony often settles in moist or decayed wood (leaks, condensation, poor air circulation). It can also establish satellite nests, for example in insulation, hollow doors or wall voids. To prevent the problem, correct the source of moisture and replace the damaged wood.
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AHead
Head equipped with strong mandibles that cut through wood to excavate the galleries.
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BThorax
Thorax evenly rounded when viewed from the side, a feature that distinguishes it from other ants with an uneven thorax.
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CPetiole
A single node between the thorax and the abdomen. Other ants have one or two nodes.
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DAbdomen
In the black carpenter ant, the abdomen bears many fine hairs, clearly visible with a magnifying glass.
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EAntennae
Elbowed antennae, as in all ants.
Worker
Workers of variable sizes (small and large), black. They excavate smooth galleries in moist or decayed wood to nest.
Queen
Larger than the workers (up to about 25 mm). She founds the colony and can live more than 10 years. She loses her wings after mating, when she starts her nest.
Winged male
Winged; its role is reproduction during the nuptial flight.
Life cycle
HOLOMETABOLOUS · 4 STAGES · ABOUT 2 TO 3 MONTHSThe queen lays the eggs in the nest. A young queen first raises a small first brood of about 10 to 20 individuals.
Legless, it is fed in the nest, first by the queen, then by the workers. This stage lasts about 14 to 25 days.
The larva spins a cocoon, in which it transforms into a pupa. The adult emerges after a few weeks.
Worker, queen or male. Winged queens and males produced in summer or fall spend the winter in the nest before their nuptial flight.
Do not confuse with
Often confused with the black field ant, which mostly nests in the soil, outdoors.
Signs of activity
Sawdust
Small piles of coarse sawdust pushed out of the galleries. The galleries themselves are clean, with no sawdust.
Galleries in the wood
Smooth, polished tunnels, often in moist or decayed wood.
Night activity
In spring and summer, workers search for food mostly at night, starting at sunset. Ants seen indoors in winter usually come from a nest inside the house.
Winged ants (swarm)
Large numbers of winged ants indoors, from late winter to spring, indicate a nest in the building.
Carpenter ants do not eat wood. Parent nests are most often found in moist or decayed wood.
Treatment
Sugar tracking bait
- 1 tsp Honey or sugar Attracts workers, which are fond of sugary liquids such as honeydew
- A few drops Water Dilutes the honey or sugar into a syrup
- 1 Small piece of cardboard Serves as a tray to place near the trails
- Dilute the honey or sugar with a few drops of water to make a syrup.
- Place the syrup on the cardboard, near areas where ants travel, out of reach of children and pets.
- Come back after sunset with a flashlight to watch the workers feeding on it.
- Follow the workers as they leave: their route can lead to the main nest or to a satellite nest.
- Do not make a homemade poison bait with borax or boric acid: Health Canada advises against it. Use only a registered product, according to the label.
As long as the source of moisture (leak, condensation, poorly ventilated wood) is not corrected, the wood remains favourable to a new colony settling in.
Spraying the visible workers does not eliminate the colony: the product only drives them elsewhere.
If the galleries reach the joists or beams, call a pest management professional. Damaged structural wood should be replaced.
Finding the nest
Follow the workers at night: their trail can lead to the nest
At night, between sunset and about 2 a.m., follow the ant trails with a flashlight.
Tap walls, beams and floors, then press your ear against them: an active colony can make a dry rustling sound, louder when it is disturbed.
The main nest is often outdoors (tree, stump, log). Satellite nests can become established indoors.
Apply a small amount of registered insecticide dust directly into the nest or galleries, following the label. This work is often entrusted to a professional.
Prevention
- Repair leaks and moisture problems
Inspect the roof, plumbing and foundation. Moist or rotting wood attracts carpenter ants and makes it easier for them to excavate their galleries.
ZONE 1 · FOUNDATION - Keep firewood away
Store firewood as far from the house as possible, off the ground, and never stack it against the walls.
ZONE 2 · PERIMETER - Trim branches in contact
No branch should touch the roof or walls: they serve as a direct highway to the building’s entry points.
ZONE 3 · TREES - Seal entry points
Seal foundation cracks and openings around electrical wires, pipes and vents.
ZONE 4 · BUILDING ENVELOPE - Ventilate the crawl space
A poorly ventilated crawl space accumulates moisture. Ensure good ventilation to keep the wood dry: carpenter ants prefer wood with a moisture content of 15% or higher.
ZONE 5 · CRAWL SPACE
Frequently asked questions
Does the carpenter ant destroy wood?
It does not eat wood but excavates galleries in it to nest, especially in moist or damaged wood, which can weaken the structure.
How can I tell if I have them?
Large black ants active mostly in the evening, small piles of sawdust under woodwork, and sometimes a faint rustling sound in the walls.
Why are they in my home?
They mainly seek out moist or rotting wood, for example near a leak, condensation or a poorly ventilated area. A moisture problem encourages them to settle in.
How do I get rid of them?
You need to locate the nest and correct the moisture problem. Store-bought baits do not always eliminate the colony; a professional can treat the nest directly. For a solution suited to your situation, you can consult our carpenter ant extermination service.