Identification
Camponotus modoc is the dominant carpenter ant species across coastal British Columbia, and the largest ant most Metro Vancouver homeowners will ever see indoors. Workers range from 6mm (minors) to 13mm (majors), with a matte black body, reddish legs, and a single-node waist. Viewed in profile, the thorax is evenly rounded — no spines, no humps — which distinguishes them from pavement ants and most other house-invading species. Antennae are elbowed. A second species, Camponotus vicinus, also occurs locally and looks similar but often shows a reddish thorax. Reproductive swarmers (alates) emerge with wings in spring; the females shed their wings after mating, and finding discarded wings on a windowsill or bathtub is a strong indicator of an established, mature colony rather than a casual foraging trail.
Habitat in BC
Carpenter ants follow moisture. In Metro Vancouver that means cedar-shingle roofs with aged flashing, rotted fascia boards, window frames behind failed caulking, deck ledgers, hot-tub surrounds, and anywhere a roof leak has persisted unnoticed. Parent colonies are usually outside — in a dead fir, a rotting stump, or a woodpile — with satellite colonies inside the structure. North Shore homes against the forest edge in North Vancouver, West Vancouver, Deep Cove, and Anmore see the heaviest pressure, but we find active structural infestations every week across Burnaby, New Westminster, and South Surrey. Any home older than thirty years with wood-to-soil contact somewhere on the perimeter is a candidate.
Signs you have carpenter ant
- Coarse frass — looks like a mix of sawdust and insect parts — accumulating under window sills, baseboards, or deck beams.
- Large black ants (6–13mm) foraging indoors, especially at night, often along the same route for weeks.
- A faint rustling or crinkling sound inside walls or ceilings after dark, most audible in quiet rooms.
- Winged reproductives emerging indoors in March, April, or May — almost always means a mature satellite colony in the wall.
- Hollow-sounding wood at window frames, door jambs, or deck ledger boards when tapped with a screwdriver handle.
- Discarded ant wings on windowsills, in spider webs near lights, or on bathroom countertops.
Risk & damage
Carpenter ants do not eat wood — they excavate it to build galleries for the colony. Over years, a mature colony of Camponotus modoc can hollow out structural framing, joist ends, and roof rafters in a way that is not immediately visible from outside. Unlike subterranean termites, the damage is slower and more localised, but it is structural. In BC's wet climate, carpenter-ant damage almost always coexists with a moisture problem — a leaking roof, failed flashing, a neglected gutter — which means the wood is already compromised and the ants are accelerating what rot has started. Health risk to humans is minimal; they can bite defensively but rarely do. The financial risk is the concern.
Seasonality in Metro Vancouver
Metro Vancouver's carpenter-ant season runs roughly late February through mid-October, with peak activity in May, June, and July. Reproductive swarmers emerge in spring when overnight lows sit above 10°C for a week — in Vancouver this usually means mid-April to late May. Foraging peaks in the warm, dry window of July and August, when you'll see the most indoor activity. Colonies slow through fall as temperatures drop, and from November through February they're largely dormant inside their galleries. That dormant window is actually an excellent treatment period: the colony is concentrated, not dispersed, and non-repellent baits placed on known trails are carried back with high efficiency.
Treatment approach
Our approach follows Integrated Pest Management principles required under Health Canada's Pest Control Products Act. Step one is always identification and trail-tracing — we confirm Camponotus modoc (or vicinus) and locate the moisture source driving the infestation, because without fixing the water problem, treatment is temporary. Step two is a non-repellent active such as fipronil or a borate-based gel, applied along foraging trails and at galley entry points. The workers carry the active back to the queen and satellite colonies, eliminating the colony at the source rather than fragmenting it. Step three is an exterior perimeter barrier to prevent re-colonisation. We pair every carpenter-ant job with a written moisture audit — the treatment will fail without fixing the water intrusion that brought them in.
When to call a professional
If you see large black ants indoors more than twice in a week, hear rustling in walls at night, or find winged swarmers inside your home, call a professional. Retail sprays are contact-kill repellents that scatter the colony into multiple satellites and make the infestation worse. DIY is reasonable only for a casual trail on a patio with no indoor activity; once carpenter ants are inside the envelope, you need professional diagnosis of the moisture source plus a non-repellent treatment.
Prevention playbook
How to prevent carpenter ant in Metro Vancouver homes
- 1
Fix every moisture source on the envelope
Carpenter ants follow water. Before anything else, audit the roof, gutters, downspouts, flashing, deck ledgers, and window caulking for leaks. In Metro Vancouver's climate, any persistent damp-wood site becomes a candidate nest within one wet season.
- 2
Eliminate wood-to-soil contact
Keep a 6-inch gap between soil and any wood siding, deck post, or fence rail. Remove stacked firewood, rotting stumps, and leaf litter within 6 feet of the foundation — these are the outdoor parent-colony sites that seed indoor satellites.
- 3
Seal the perimeter
Caulk gaps around utility penetrations, window frames, and siding transitions with high-grade silicone or polyurethane. Pay particular attention to cedar-shingle roof returns and fascia boards on 1940s–1980s homes across Vancouver, Burnaby, and North Delta — the highest-risk stock.
- 4
Trim vegetation off the building
Cut back shrubs, climbing vines, and tree branches so nothing touches the roof, soffits, or siding. Carpenter ants use branches as direct foraging highways into attics — a common entry path for North Shore homes.
- 5
Never spray visible ant trails with retail repellents
Pyrethroid sprays from the hardware store are contact-kill repellents. They scatter the colony into multiple satellite sub-colonies and make the infestation dramatically worse. If you must act before a professional arrives, wipe trails with plain soapy water and observe — never spray.
- 6
Schedule a spring inspection on older homes
For any home built before 1985, or any home with a known moisture history, book an annual exterior inspection in early April — before the reproductive swarm. Identifying satellite colonies before swarmers appear indoors prevents the worst structural damage.
The Wild Pest service
See our Carpenter Ant treatment page
Transparent pricing, 60-day return guarantee, same-day response across Metro Vancouver. Every treatment is documented with photos and service notes.
Frequently asked questions about carpenter ant
How do I tell carpenter ants from regular black ants?+
Size and shape. Camponotus modoc workers are 6–13mm — much larger than pavement ants or odorous house ants (2–4mm). Viewed from the side, a carpenter ant has an evenly rounded thorax with no humps or spines, and a single-node waist. If you're finding large black ants indoors in Metro Vancouver, it is almost certainly a Camponotus species.
Why do I only see them at night?+
Carpenter ants are primarily nocturnal foragers, especially in warm weather. Workers leave the nest after dusk, travel along established trails to food and water sources, and return before dawn. You can confirm a colony's direction by turning off interior lights, waiting 20 minutes, then following a single flashlight beam along baseboards — you'll usually pick up the trail.
Is carpenter-ant damage covered by home insurance in BC?+
Almost never. Most BC homeowner policies exclude pest damage, including carpenter ants, classifying it as preventable maintenance. The exception is consequential damage — if a carpenter-ant gallery contributes to a sudden structural failure, some insurers will cover the collapse but not the ant work. Treat it as out-of-pocket and prioritise the moisture fix.
Can I spray the trail myself?+
Don't. Retail contact-kill sprays are repellents — they eliminate the workers you see but signal the colony to fragment into multiple satellite nests, making your problem worse and harder to treat. Professional treatment uses non-repellent actives the workers carry back to the queen. Spraying a visible trail is the single most common mistake we see on arrival.
We live near the forest in North Vancouver — are we higher risk?+
Yes. North Vancouver, West Vancouver, Deep Cove, and Anmore see the highest carpenter-ant pressure in Metro Vancouver because parent colonies live in the adjacent Douglas-fir and cedar forest. Homes within 30 metres of the forest edge should assume annual pressure and consider our quarterly plan with a spring carpenter-ant focus.
How long does it take to eliminate a colony?+
A typical Camponotus modoc satellite colony collapses within 2 to 4 weeks of proper non-repellent bait placement. A large multi-satellite infestation tied to a chronic roof leak can take 8 to 12 weeks and requires the moisture source to be fixed mid-treatment. We include a 60-day guarantee and re-treat at no cost if activity reappears in that window.
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