One has a common name of pavement ant. This is an ant that enjoys warmth and can be found nesting next to or under paved surfaces outdoors. This is a common ant found with homes built on a slab with the heating and cooling system below the slab. The ground remains warm near the duct work and can allow the ants to remain active. As any ant colony would, foraging for food is pretty typical. In cold weather, when the soil is frozen, foraging is going to take place in the home.
Extension gets those calls where all of a sudden ants are found by the hundreds (it only seems to be the thousands) swarming over the kitchen counters or trailing across open space headed for the dry pet food station.
Ants are routinely sending out scout ants in the hunt for a food source. This time of year with all the goodies being baked and brought home from office parties and left on the counter, we create a great buffet. Once that scout ant finds something good to eat, the message gets back to the colony and the march begins.
To prevent ants from discovering your treats, keep them in tight-sealing containers. If you find the dry pet food being eaten, remove the source by feeding the pets and not leaving leftovers. Once the ants cannot find food or continue to feed, they will look elsewhere for another source of food.
You really cannot use any sprays around the kitchen counters and pet food stations, so sanitation is your best approach. If you knew the ants were coming in from the outside, a foundation spray outdoors could be used. Ant baits can be used and usually provide control without having to use additional sprays. Since the ants follow a predetermined trail from the nest to the food source, washing that area with soap and water will greatly reduce the infestation as they get confused about the route to take.
Richard Hentschel is a Horticulture Extension Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Stay tuned to more garden and yard updates with the Green Side Up podcast at go.illinois.edu/greensideup.