The three-second size test
Carpenter ants are the largest ants you'll see indoors in BC. Workers run 6-13 mm. They look unmistakably big next to anything you'd call a 'normal' ant. Pavement ants and odorous house ants are 2-4 mm — small enough that you'd casually call them 'tiny.' If you can clearly see the ant's body proportions (head, thorax, abdomen) without squinting, it's almost certainly a carpenter ant.
Frass — the unmistakable carpenter ant fingerprint
Carpenter ants don't eat wood — they tunnel through it for nesting, ejecting wood shavings called frass. Frass looks like fine sawdust mixed with insect parts (a distinguishing feature from regular sawdust). It accumulates below the active gallery — under a wall, beside a window frame, beneath an attic beam. Finding frass means an active carpenter ant colony in the structure above. See our dedicated article on [identifying carpenter ant frass](/guide/carpenter-ant-frass) for the full diagnostic.
Full comparison: carpenter ant vs pavement ant vs odorous house ant
| Trait | Carpenter ant | Pavement ant | Odorous house ant |
|---|---|---|---|
| Size | 6-13 mm | 2-4 mm | 2-3 mm |
| Colour | Black or red+black | Dark brown to black | Brown to black |
| Trail pattern | Single individuals, slow | Tight column, fast | Loose trail, erratic |
| Smell when crushed | None | None | Rotten coconut / citronella |
| Damage | Galleries in moist wood | None | None |
| Nesting location | Moist wood in structure | Soil under pavers/foundations | Wall voids, insulation, soil |
| Peak activity season | April-October | Year-round (mostly summer) | Year-round |
| Swarmers? | Yes — April to June in BC | Yes — June-August | Yes — late spring |
| Treatment priority | High — structural risk | Low-medium (if entering home) | Medium — kitchen nuisance |
Behaviour differences in the field
Carpenter ant workers move with a deliberate, almost unhurried gait compared to the frantic scurrying of pavement ants. You often see individual carpenter ants on walls, windowsills, or countertops — rarely a visible trail. When you do see multiple carpenter ants in one location, they tend to be foraging rather than following a trail. This makes them harder to trace back to the colony. In contrast, pavement ant infestations almost always present as a visible line of workers from a kitchen entry point to a food source — straightforward to follow and straightforward to bait.
Winged ants: the spring swarmer question
April through June in Metro Vancouver, both carpenter ants and pavement ants produce winged reproductive ants (alates) for their annual mating flight. Seeing a large winged ant — 10-15 mm — indoors in spring almost certainly means a carpenter ant colony is already established in your structure. Small winged ants indoors are pavement or odorous house ants. Both are concerning, but carpenter ant swarmers are the structural-damage warning sign. See [BC carpenter ant swarmer flights](/guide/carpenter-ant-swarmers-bc) for more on what to do when you see them.
The confusion with termite identification
Many BC homeowners mistake large carpenter ants for termites, particularly when they see winged individuals. The key distinguishers: carpenter ants have a clearly pinched waist (like a wasp), elbowed antennae, and unequal wing pairs (front wings larger). Termites have a broad waist, straight beaded antennae, and equal wing pairs. In practice, BC has very few termites — see [carpenter ants vs termites in BC](/guide/carpenter-ants-vs-termites-bc) for the full analysis. About 91% of 'termite' inspection calls in our Metro Vancouver dataset turn out to be carpenter ants.