Besides being objectionable by their presence, carpenter ants damage wood by hollowing it out for nesting. They excavate galleries in wood which have a smooth, sandpapered appearance. Wood which has been damaged by carpenter ants contains no mud-like material, as is the case with termites. Shredded fragments of wood, similar in appearance to coarse sawdust, are ejected from the galleries through preexisting cracks or slits made by the ants. Oftentimes, however, the excavated sawdust remains hidden behind a wall or in some other concealed area.
Carpenter ants nest in both moist and dry wood, but prefer wood which is moist.
Nests are especially common in moist, hollow spaces such as the wall void behind a dishwasher, or in a hollow porch column. Since there often will be no external signs of damage, probing the wood with a screwdriver helps reveal the excavated galleries. Another technique for locating hidden nests is to tap along baseboards and other wood surfaces with the blunt end of a screwdriver, listening for the hollow sound of damaged wood. Carpenter ants may establish nests in a number of different locations. It is important to realize that these locations can be either inside or outside the structure .