Carpenter ants are the most likely culprits because they like to nest in wood and because they remove any dead ants from their nests. When an ant dies, it releases an odor that signals to the other ants to remove it. Carpenter ants are notorious for creating small piles of sawdust and dead ants, known as frass, outside their nests. Since other ants also can exhibit this behavior, take a few of the dead ants to a county extension office for identification before you attempt any treatments.
Carpenter ants like to build nests especially in rotted wood. If your home has had any problems with a leaking roof or excess moisture in your attic, then that is likely to be the site of the nest. Homes built with or near lots of wood are more prone to carpenter ant infestations than other homes, according to Laurel Hansen, Ph.D. of Spokane Falls Community College. Hansen found homes built with cedar or plywood siding, or wood frames, or those that were surrounded with vegetation were more prone to carpenter ant colonization. Other common elements included crawl spaces, a moderately to gently sloping roof and homes built between 5 and 25 years ago.
Treating carpenter ants nesting in your home is difficult for several reasons. Nests found inside usually are satellite nests built by a larger parent colony nesting outdoors. You must locate and treat the satellite and parent nests, which is the second problem. Carpenter ant nests can be almost impossible to find. Baiting is an option, but not recommended for carpenter ants because they have finicky eating habits. They don't eat the bait long enough for it to affect the entire colony. If you do try baits, use baits labeled for indoor use against carpenter ants, and that contain abamectin B1, fipronil, hydramethylnon or sodium tetraborate decahydrate specifically.
When dealing with carpenter ants nesting inside your home, your best option is to call a professional pest control company. Most of the insecticidal dusts labeled for use against carpenter ants are not available commercially. Select a company that will make the effort to find the indoor and outdoor colonies. Don't use one that suggests a monthly spray, or injects chemicals into the soil or randomly in the walls because these treatments are rarely effective and more expensive, according to Barb Ogg, an extension educator with the University of Nebraska.