All ants live in colonies, consisting of an egg-laying female (queen), short-lived males, and workers (sterile females). The ants you see foraging in your garden or kitchen are workers. Workers that find food communicate with other workers by depositing a chemical message on the substrate as they crawl back to the nest. Although we cannot smell it, this "trail pheromone" sticks to the substrate for long periods of time and helps other ants find the food at the end of the trail.

Treatment

The best way to control ants that inhabit a dwelling is to find the nest and destroy it. Insecticide sprays inside the home will kill some of the worker ants, but unless the entire nest is treated, the queen will continue to produce additional members of the colony.

The most likely places to find carpenter ant nests are where wood has been wet and weathered, such as rotting timbers about the foundation, window sills, porches, around leaky plumbing, and in rafters under a leaky roof. 

The best treatment is to apply an insecticide directly into the nest. It is also important to replace damaged or decayed wood, and if possible to eliminate any moisture problems. Baits may also be effective if applied where ant activity is seen.