The moisture ant is small in size, generally ranging from 1/8 inch to 3/16th of an inch in length and vary in color from yellowish to dark brown. These ants feed on fungus in decaying wood. This ant is actually known as the cornfield ant, however my father did a great deal of research on this ant in the Pacific Northwest as these ants were found in great numbers in decayed walls around bathroom shower stalls, and other heavy water laden wood portions of structures. His research in the 1950(s) along with setting government standards for structural pest inspections in FHA owned houses caused the name he applied to them to become a common name in the industry. These ants feed on other insects, honeydew from aphids, and fungus growth that is found in decaying wood matter. In nature they can be found under fallen trees, in stumps, or any organic matter that may have accumulated on the ground. When this ant is found in the structural portion of your home it is usually near a water source of some kind. It could be a leaking plumbing wall, a shower stall that the grout has worn away, in the floor area around the tub, or toilet. Possibly in a wall where a roof gutter has backed up, or in a wall where the outside soil is touching the siding or even several inches above the bottom of the siding. They can be found in the substructure area under your home in form boards that were not removed during construction, in support posts that have a wood to soil contact. Any area of your home that has water touching the wood can attract the Moisture ant. This ant does not destroy the wood, as they are only there because they are attracted to wood that has deteriorated. In a sense they are a flag that should be raised to alert you of the problem.
A thorough examination of the area in question should be performed, and any corrective measures should be followed up with. The infestation is generally a localized one, so if the damaged wood is removed, the moisture problem corrected, and the infested areas treated, this will eliminate the problem. Sometimes these ants can be coming up through a crack in a concrete slab under a wall. In this case correction of a water problem may not be possible, however removing the carpet or floor covering and sealing the joint that the ants are coming through can fix the problem.