How can I tell if these ants that have suddenly appeared in our house are carpenter ants. They’re dark and they seem pretty big, so I’m worried. L.P., Westminster, MA

It’s going to be very difficult to reassure you without actually seeing the ants. Carpenter ants are the largest ants that get into structures but some other species may appear large as well, especially if you are looking at a reproductive ant instead of a worker. First off, you need to contact a pest control professional both for an identification (save some ants) and for an inspection of your home. Even if the ants turn out not to be carpenter ants, I’m guessing that you don’t want them in your house; our experts can assess the situation and eliminate the ants, no matter what.

Carpenter Ant Identification – The worker ants are large, ¼ to ½ inch long and usually solid black. Workers may appear in a range of sizes and reproductive can be quite large and winged. If you look at a worker ant in profile under magnification, you could see that it has a uniformly rounded thorax. This is rather unique as most ants have an uneven, bumpy thorax. (The thorax is the middle of the ant’s three main body parts and is between the head and the abdomen.)

Any Wet Wood or Water Damage? – Carpenter ants don’t eat wood but they do hollow it out for their nest galleries. They prefer soft wood that is easily chewed so they are drawn to wood that has been softened by decay or moisture. Although they may first attack wood associated with a plumbing leak, roof leak, or excess condensation, they can then move into dry wood as well. 

Any Piles of “Sawdust?” – When carpenter ants are constructing their galleries inside wood, they take great pains to keep the galleries clean and dump wood shavings, dead ants, bits of insulation, and other debris out of the nest through slit-like openings in the wood. At first glance, this carpenter ant dump may look like little piles of sawdust. Often the nest site can be found just above the dump piles but when the nest is in wood inside a wall void or other inaccessible area, this evidence may never be seen.

For more info on carpenter ants, see these Colonial blogs:

• Carpenter Ant Basics – What You Need to Know
• Why Are Carpenter Ants a Concern?
• Will These Ants Start a Nest Inside My House?
• Carpenter Ants May Not Be Seen, But Damage Continues

Whether carpenter ants or another pest species, the ants are not necessarily nesting in your house. They could just be foraging in from an outside nest looking for food or moisture. A professional can track the ants and answer that question. For more on how Colonial treats carpenter ant infestations, see Carpenter Ant Control under Services.