Lasius spp.

Characteristics – 
Size:  1/8-inch in length.

Color:  Dark brown, similar in appearance to a number of different house-infesting ant species.

A person experienced in ant identification is usually required for proper identification

Behavior –  Moisture ants will invade homes from nests in the yard while foraging for food. Occasionally, an outdoor colony will relocate inside in the bathroom or kitchen where a water leak is present. This ant often carries soil into the building which it uses to construct a "carton" nest. Carton nests resemble hard clods of soil and may be fashioned around a water pipe or onto a wooden sill plate or wall stud. 

Habitat –  The correct name for moisture ant is actually the cornfield ant. This species most commonly nests in the soil of lawns and fields. Once inside, nests are typically established near water leaks, hence the nickname "moisture" ants. The appearance of this ant inside homes most commonly occurs in the Pacific Northwest states of Washington and Oregon, although the cornfield ant is found throughout the north and Midwest parts of the country. 

Tips for Control –  For those situations involving foragers invading from outside, sealing exterior cracks and holes in the foundation and around windows and doors is helpful. Indoor colonies are best controlled with treatment by a professional combined with steps to repair the water leak and dry out the moist area.