Carpenter ants get their common name from their habit of making their nest in wood. They excavate the wood but they do not eat it. Outdoors, these ants nest in trees, fallen logs, and rotting stumps. There are almost thirty species of carpenter ants in the U.S., but fewer than ten species cause problems for homeowners.
Carpenter ant workers usually gather insects and honeydew for the colony to eat. When food is hard to find or the weather is too extreme, the workers might forage into homes. If they find source of food or water, the carpenter ant workers often make a nest nearby.
Carpenter ants make two kinds of nests. They make a nest where the main colony lives. There is usually only one queen and she stays in the main nest. The workers often make satellite nests inside the home. The satellite nest might have a few hundred workers and may have some immature ants. The workers move in trails between the main nest, the satellite nests, and the food or water sources.
It is very common for carpenter ants to make their satellite nest in hollow or void spaces. They frequently nest inside of wall voids, especially near doors and windows. They also make their nests in the bases of cabinets and in attics. People report hearing the rustling sounds of carpenter ants moving around inside the walls.
If the carpenter ants move the main nest indoors, it is often into a place where there has been a moisture problem. The workers will excavate damp, decaying wood in order to make a nest. It is common to find carpenter ants nesting in wood under roofing shingles, inside bathroom walls, behind kitchen sinks or laundry equipment, and in damp basements or crawl spaces.
When the workers are creating the nests, they remove bits of wood that look like wood shavings. The galleries that the ants make are smooth and clean. There is no dirt in the galleries as there is in termite galleries. The workers push the wood debris out of the nest. Homeowners often find small piles of this debris on floors or windowsills. Many times they see the piles of debris before they see any of the ants.
Carpenter ants also nest in the foam sheathing that homebuilders use in construction. The ants make their galleries inside the foam. Homeowners often find small pieces of foam on the ground beside the foundation.