Rising Temperatures and the Rise of the Carpenter Ant

Carpenter ants are Ontario's largest native ant species, and they're one of the most misunderstood. Unlike termites, carpenter ants don't eat wood — they excavate it, removing material to create smooth-walled galleries for nesting. The distinction matters less when you're looking at structural damage, but it matters a great deal for how the problem is treated.

Warming springs have extended the active season for carpenter ants significantly. They typically become active when temperatures consistently exceed 10°C — which in the GTA has been happening weeks earlier than historical averages in recent years. An earlier start means a longer foraging season, larger colony sizes by midsummer, and more opportunity for satellite colonies to establish inside structures.

The primary nest of a carpenter ant colony is almost always outdoors — in a dead tree, a rotting stump, or a pile of untreated wood. Satellite colonies, which house workers and brood, are commonly found inside structures. Entry is typically through small gaps around windows, doors, utilities, or damaged wood. Moisture-damaged wood is strongly preferred — a slow leak under a sink or around a roof flashing creates ideal nesting conditions.

Treating only the interior of the home is rarely effective for long-term control. A complete carpenter ant program involves locating the primary outdoor nest when possible, treating all active interior galleries and trails, sealing entry points, and addressing any moisture sources that created attractive nesting conditions. Follow-up is important because satellite colonies can survive independently and rebuild.

If you're seeing large black ants — roughly 6–12mm — inside your home, particularly in spring or early summer, it's worth having the property assessed. A single worker ant in the kitchen might be a forager from an outdoor colony; a consistent trail, or the presence of sawdust-like frass, usually indicates an established satellite colony that requires treatment.