Reviewed by William "Willy" Vizcarrondo, NYS Certified Pesticide Applicator (C1825832). Updated September 23, 2026.
The black carpenter ant is Long Island's most common wood-nesting insect. It doesn't eat wood the way termites do; it hollows out damp or decayed wood to nest in, and its presence in a house almost always means water is getting in somewhere.
| Size | Workers 1/4 to over 1/2 inch, several sizes in one colony |
|---|---|
| Color | Black, sometimes with reddish legs |
| Look-alikes | Termite swarmers (straight antennae, thick waist, equal wings), pavement ants (much smaller) |
| Where you'll find it | Porch posts, window and door frames, deck framing, siding, floor joists, bathrooms and kitchens with leaks |
| Active on Long Island | May through October, peak July; indoor sightings in late winter mean a nest in the house |
| Danger level | Structural damage over time, moisture indicator |
Carpenter ants are active outdoors from May to October and peak in July; large black ants indoors in February or March mean the colony is living in the house.
Large black ants, up to half an inch or more, with a narrow pinched waist, elbowed antennae, and a smooth rounded back. Winged swarmers appear in spring and look like flying ants with front wings longer than the hind wings.
Termite swarmers, which show up around the same time, have a thick waist, straight antennae, and two pairs of equal-length wings nearly twice the body length (Penn State). The tunnels tell you too: carpenter ant galleries are clean and smooth and cut across the grain; termite tunnels follow the grain and are packed with mud (Rutgers).
A mature colony, 3 to 6 years old, holds 2,000 to 3,000 or more workers plus satellite nests, and it keeps expanding galleries in the wet wood it lives in (CCE Nassau). The damage is slower than termites but it's real, and the wood it chose was already compromised by water.
Cornell Cooperative Extension calls carpenter ants an indicator organism: they're telling you about a leak, condensation, or wood-to-soil contact you haven't found yet.
Killing the ants you see doesn't touch the colony. Spraying drives them deeper, and baits take weeks to reach the brood and the queen (Rutgers). The colony has to be located, which is the hard part, and the moisture source has to be fixed or they come back (CCE Nassau).
Homeowners can and should fix the leak, replace rotted wood, and cut back branches touching the house. Finding and treating the nest is the job to call for.
We find the nest and any satellite nests, treat them directly, bait the trails, and show you the moisture problem that let them in. Carpenter ant treatment carries a 6-month written guarantee.
Related answers
Carpenter ants have a pinched waist, bent antennae, and front wings longer than the back wings. Termites have a thick waist, straight antennae, and four equal wings. Ant tunnels are clean; termite tunnels are muddy.
Because the colony is in the house. Outdoor carpenter ants aren't active in winter, so indoor sightings in January through March mean a nest in a wall, a window frame, or under a bathroom.
Almost always. They nest in wood that's damp or partly decayed. Common spots are under leaking windows, around bathroom plumbing, in porch posts, and in deck framing.
No. As long as the wood stays damp the colony stays and grows, and it sends out satellite nests into nearby wood.
Think you have carpenter ants? Call (516) 509-6001 for a free written quote.