Jeffrey Hahn, Asst. Extension Entomologist
Winter is not a time when you typically expect to encounter ants in your home. However, it happens more often than you might think. One of the more common ants found in homes and other buildings is pavement ants. This ant is 1/8th inch long and is reddish brown, although it can range in color from light brown to dark brown to almost black. With magnification you can see that this ant has a two-segmented petiole (the waist between the thorax and the abdomen) and two short spines projecting from the thorax.
Photo 1: Pavement ant worker. Note the two-segmented petiole and two small spines on the abdomen.
Pavement ants like to nest in the soil under or besides objects, such as stones, bricks, sidewalks, and driveways. They can also nest under the concrete slabs of homes as well as in wall voids. They typically nest near a heating source which allows the ants to be active during winter. They can follow pipes that go through slab to move up into the living quarters of homes thorough expansion joints, under baseboards and floor registers. Sometimes large numbers of winged pavement ants are found which are the reproductives of the colony, i.e. females and males.
Pavement ants can infest foods; they like protein and grease, such as meats, cheese, dead insects, dry pet food, and peanut butter, as well as a variety of sweets. Other than that, pavement ants are mostly annoying and are not particularly damaging to homes.
If you are finding pavement ants in your home, try to determine from where they entering. If you can determine they are moving through a crack, e.g. in an expansion joint, try to seal it to help keep pavement ants out. If you are not able to find how they are getting into your home, then try baiting them.
Select a bait that is effective for grease feeding ants and place it where you are commonly finding them. Don't be surprised if there is an increase in the number of workers that are around the bait. That's good, the more ants that take bait back to the nest, the more likely you can eliminate it. Don't spray the foraging workers. It doesn't have any impact on the colony and will also lessen the ability of the workers to take bait back to the nest.
If you are not successful in your efforts to get rid of pavement ants or you would rather have someone control them for you from the start, talk to a professional pest management service about treating your ants.
Not all ants found indoors during winter will be pavement ants. People can also potentially see carpenter ants, Pharaoh ants, yellow ants, and thief ants in their homes during the winter. Their habits differ as do the methods for treating them. If you have any doubt as to what kind of ant problem you have, get them identified them by an expert.