One of the many things our team looks for when inspecting a home is the presence of wood-boring insects. In the wild, many wood-boring insects are beneficial because they assist in the conversion of dead wood to soil. However, in our homes they are some of the most dangerous pests, as they can compromise the home’s structural integrity. Depending on the climate of the region, certain wood-boring insects may be more or less prevalent. In Northern Michigan, the carpenter ant, which thrives in our relatively cool climate, is the most widespread pest of the wood-boring variety. This article seeks to be a primer on this species and its relationship to the home.

Carpenter ants are indigenous to nearly the entire continental United States but are most prevalent in forested areas. Unlike termites, the carpenter ant does not have the ability to consume wood. However, they do chew through wood (preferably dead & damp wood) and construct their nests in the chewed out portions of the wood, known as “galleries”.

The presence of large (1/2 inch), wingless, dark-colored ants inside a home is usually the first sign of an infestation. However, this does not necessarily mean that a nest is present indoors. The nest may actually be located outside, near the building. Thus, foraging workers from the nest may be entering the structure in search of food and water. These worker ants, which usually emerge at night, will feed on meats and foods containing sugar and fat. During the summer, homeowners can use a flashlight to look for foraging workers at night. Check basement, attic, garage and building exterior from May through July between the hours of 10:00 p.m. and 2:00 a.m. It may be possible to follow the ants back to their nest or discover where they are entering the house. If numerous winged reproductive ants are found at windows inside the house, they probably came from an indoor nest.

The indoor nest(s) may have originated from one or more parent colonies outside the home. The parent colony is often located in a tree, log, or waste wood within 100 yards of the house. Workers travel between the satellite and parent colonies. To eliminate the ants, the parent and the satellite nests must be found and eliminated. Common indoor nest locations include porch pillars and supporting timbers, sills, girders, joists, wall studs, window and door casings, and under insulation between ceiling joists or wall studs. Check areas where the wood may be wet or damp because of poor ventilation, a leaking roof, defective flashing, overflowing or leaking gutters and downspouts, condensation from water pipes, or leaking bathtubs, showers, and appliances. In homes, the ants typically do not excavate wood for nest construction, but make their nests in hollow areas of ceilings, walls, or floors. They will tunnel through sound structural timbers to gain access to a void on the other side, but this has little effect on the structural integrity of the timber.

Homeowners should watch for ants that are foraging indoors and try to find their nests. Look for piles of coarse, stringy wood particles, dead insect parts and other debris that are sifting from cracks in the siding, behind moldings, in the basement and attic, and under porches. Because carpenter ants do not consume the wood as food, excavated particles are dumped outside the nest. Unlike termites, the tunnels or galleries of carpenter ants are smooth-sided and contain no soil particles or fecal pellets. Satellite colonies within homes can sometimes be located by listening for a rustling sound in walls and ceilings using a stethoscope or inverted water glass to hear the ants.