Identification
The carpenter ant is recognized by its large size (6 to 13 mm), its glossy black body and its single-node petiole. It does not eat wood: it excavates smooth, clean galleries in it to house its colony. When that excavation reaches the joists or the main beams, it can compromise a building's structure within a few years.
A queen that lives 25 years, a colony of at least 10,000
A mature colony has 3,000 to 10,000 workers and survives as long as its queen does. As long as the queen is not eliminated, the infestation comes back. That is why surface insecticides often make the situation worse: they scatter the workers without ever reaching the royal chamber.
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AHead
Large head with powerful mandibles used to excavate wood and cut up prey.
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BThorax
Thorax in a single arched, convex piece - the distinctive trait that sets it apart from the common black ant.
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CPetiole
A single node between the thorax and the abdomen - the key to identification: carpenter ants have only one node.
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DAbdomen
Segmented abdomen, often curved, covered in fine silvery hairs visible with a magnifying glass.
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EAntennae
Elbowed antennae with 12 segments, a reliable identifying trait of Quebec's ants.
Worker
Entirely black body, 6 to 13 mm. Excavates damp wood to build the galleries of the nest. The one most often seen.
Queen
Larger (16-20 mm), she founds the colony and can live up to 25 years. Rarely seen outside the nest.
Winged male
Winged, lives only a few days. Its sole role: reproduction during the nuptial flight (May to July).
Life cycle
Holometabolous · 4 stages · 6 to 10 weeksLasts about 2 weeks. Laid by the queen in the deep galleries, sheltered from light and moisture.
No legs and no eyes. Fed by the workers on secretions and decomposed insects.
Enclosed in a silken cocoon. Complete transformation into an adult in 3 to 4 weeks.
Worker, queen or male. The adult no longer grows once it emerges from the cocoon.
Do not confuse
Often confused with the black field ant, a species that is nonetheless harmless to structures.
Signs of activity
Wood sawdust (frass)
Small piles of fine sawdust mixed with insect debris, pushed out of the galleries by the workers. Look at the base of walls, doors and window frames.
Galleries in the wood
Polished, smooth tunnels excavated along the grain. Often in damp beams, floor joists or exterior door frames.
Nighttime activity
Faint scratching audible at night inside the walls or under the floor. The workers are most active between 10 p.m. and 3 a.m.
Winged ants (swarm)
Winged queens and males appearing between May and July, often near lit windows, a sign that the colony is mature (3 to 5 years old).
Carpenter ants do NOT eat wood; they excavate it to house their colony. The wood must already be weakened by moisture for them to move in.
Treatment
Borax & icing sugar bait
- ½ tsp Borax Natural insecticidal agent, a gut disruptor
- 1 tsp Icing sugar Attracts the ants and carries the bait back to the queen
- A few drops Water Binds the ingredients into a thick paste
- Mix the borax and the icing sugar in equal parts in a bowl.
- Add a few drops of water to form a thick paste.
- Place small balls near the ant trails - never within reach of children or pets.
- Do not kill the ants you can see: they act as carriers to contaminate the queen and the colony.
- Replace the bait every 2 to 3 weeks until they disappear completely.
A colony always comes back if the moisture source is not corrected - a leak, condensation or poorly ventilated wood.
A surface insecticide scatters the colony and makes locating the nest far more difficult.
If the galleries reach the joists or the main beams, call a certified technician immediately.
Find the nest
Follow the workers at night, they always return to the main nest
In the evening between 9 p.m. and 11 p.m., follow the trails with a red flashlight (less disruptive).
Tap on walls, beams and floors - a hollow sound or a crumpled-paper sound reveals internal galleries.
The main nest is often outdoors (a stump, firewood). Satellite nests establish themselves indoors.
Inject boric acid powder or a dry powder insecticide directly into the galleries you have identified.
Prevention
- Repair leaks and moisture
Inspect the roof, the plumbing and the foundations. Damp or rotten wood is the leading cause of infestation.
Foundations - Move the firewood away
Store firewood at least 3 metres from the house, raised off the ground on a pallet or metal supports.
Perimeter - Cut back branches in contact
No branch should touch the roof or the walls - they act as a direct highway to the building's entry points.
Trees - Caulk the entry points
Seal the cracks around electrical wires, pipes and window frames with silicone caulking.
Envelope - Ventilate the crawl space
A poorly ventilated crawl space accumulates moisture. Ensure cross-ventilation to keep the wood below the 19% moisture threshold.
Crawl space
Frequently asked questions
Do carpenter ants destroy wood?
They do not eat wood but tunnel galleries into it to nest, especially in damp or damaged wood, which can weaken the structure.
How do I know if I have them?
Large black ants active mainly in the evening, small piles of sawdust under the woodwork, and sometimes a faint rustling inside the walls.
Why are they in my home?
They seek out damp wood: window frames, decks, areas with leaks. A moisture problem encourages them to move in.
How do I get rid of them?
You have to locate the nest and correct the moisture. An exterminator treats the nest and the perimeter, because baits alone are rarely enough.