Reviewed by William "Willy" Vizcarrondo, NYS DEC Certified Commercial Pesticide Applicator C1825832. Updated September 23, 2026.
Short answer
Follow the workers after dark, look for coarse sawdust, and check the wet wood. Carpenter ants are most active between sunset and midnight, they push sawdust out of the nest through cracks, and they nest in wood that's damp from a leak, a roof edge or a window. Where you see ants in the kitchen is usually a foraging route, not the nest.
Because carpenter ants travel. University of Minnesota's extension notes workers travel up to 100 yards from a nest in search of food, and Penn State notes the parent colony is usually within 100 yards of the house, often in a tree, stump or woodpile outside. The ants in your kitchen at night are foragers on a route from a nest, which may be a satellite nest in the house or the parent colony outside. UC IPM describes the setup: several satellite nests can be associated with a single parent nest where the queens live, with the satellites in wall voids, hollow doors and insulation indoors. Killing the ants on the counter doesn't touch either one.
Go out with a flashlight after the sun goes down. UC IPM notes carpenter ants are most active after sunset, and Minnesota's extension suggests a red-filtered flashlight between sunset and midnight. Put out a little sweet bait, a spot of honey or sugar water, or protein such as tuna packed in water, and watch which way the ants carry it. UC IPM's advice is to follow the workers back to their nest. They'll head for a gap under a baseboard, a window frame, a door casing or the space behind a dishwasher, and that's the direction of the nest. Then listen: both UC IPM and Minnesota's extension describe a faint, dry rustling sound in walls, floors or woodwork from an active colony, easiest to hear at night with your ear to the wall.
Anywhere wood stays wet. Penn State notes carpenter ants will not infest sound wood with a moisture content under 15 percent, so the nest is where the water is: under a leaking window or skylight, behind a bathroom wall, in the roof edge and soffit where gutters overflow, in a deck ledger against the house, in a door frame at grade, in a porch column, in the subfloor around a tub. Minnesota's extension lists moist or decayed wood near bathrooms, under roofing, in wall voids and in foam insulation. The tell is the sawdust: coarse, fibrous shavings, often with insect parts in them, piled below a crack. Find the pile, and the nest is above it.
The Long Island nest is usually in the roofline or a window. In the older wood-frame houses on the North Shore, Huntington, Cold Spring Harbor, Setauket, it's the fascia and soffit where a gutter has been overflowing for years, or a bay window that never got flashed right. In the Nassau capes and splits it's the bathroom wall over a slab and the sliding door frame to the deck. We track the ants at dusk, open the void where they're going in, treat it, and then look for the parent colony in the yard, because a satellite nest with the parent still out there refills. Carpenter ant treatment carries a 6-month guarantee and the estimate is free.
Related
Maybe, and maybe they're just foraging from outside. A few large black ants in spring and summer can be workers coming in from a nest in a tree or stump. Ants in the house in winter, or winged ants indoors, mean a nest in the structure; Minnesota's extension is direct that seeing carpenter ants indoors in winter means there is an inside nest.
Yes. UC IPM lists insulation among the indoor nesting sites, and Minnesota's extension specifically names foam insulation. Foam board behind siding, in a rim joist or in a finished basement wall is a favorite, especially where it's damp, and there may be very little sawdust.
You can treat that nest, but you'll usually miss the rest. Minnesota's extension notes spraying foraging workers is not effective because most ants forage outside and never contact the product, and satellite nests connect to a parent colony that will send more workers. Baits can work but take weeks or months. A professional treats the nest, the void and the parent colony.
Still not sure? Call (516) 509-6001 and we'll tell you what you're dealing with.