Carpenter Ants vs Regular Ants: What's the Difference?

By the Windy City Exterminators editorial team. Reviewed 2026-11-03.

So you found a trail of ants marching along your kitchen baseboard. Now you're staring at them, trying to decide if this is a five-minute fix or a five-thousand-dollar problem. I get this question a lot from folks around the Chicago suburbs, usually in early spring when things start waking up. The difference between "mildly annoying" and "call someone now" comes down to a handful of visual and behavioral clues. Let's get into them.

Size and shape: the first giveaway

Carpenter ants are noticeably bigger than most household ants, usually somewhere between 1/4 inch and 1/2 inch long, while pavement ants or odorous house ants top out closer to 1/8 inch. That size gap alone is often enough to make an experienced eye suspicious.

But size isn't the only tell. Honestly, it's not even the most reliable one, because carpenter ant colonies have workers of different sizes, something called polymorphism. A minor worker might be small enough to fool you into thinking you've got an ordinary house ant. So look at the body shape instead.

Carpenter ants have one node between the thorax and abdomen, and that thorax is evenly rounded from the side, almost like a smooth little hill. Regular household ants, especially the pavement ant wedged in sidewalk cracks, tend to have a bumpier thorax, uneven along the top, and some species have two nodes instead of one. It's a small detail. Once you've looked at a few under a magnifying glass, though, it becomes second nature to spot.

The waist matters too. Carpenter ants have a distinctly pinched waist, narrow and almost wasp-like, connecting thorax to abdomen. Regular ants tend to look more uniform front to back, without that dramatic hourglass shape.

Behavior: what they're actually doing in your house

Here's where most homeowners get tripped up, and where I spend most of my time explaining things on service calls. Carpenter ants excavate wood to build nests, but they don't eat it. That's a termite thing. Carpenter ants are after protein and sugar, same as most ants, and the wood is just real estate.

This changes what you should look for as evidence. Mud tubes running up a foundation wall, something pencil-width and earthen looking, mean termites, not carpenter ants. Carpenter ants leave frass instead: a sawdust-like material that's actually wood shavings mixed with bits of dead ants and insect parts, usually pushed out through small slit-like openings in the wood. Find little piles of what looks like fine sawdust near a windowsill, a deck post, or behind a bathroom tile, and that's often your first solid clue.

Regular household ants don't do any of this. Pavement ants nest in soil, under slabs, in driveway cracks. Odorous house ants nest in wall voids or under mulch and give off a smell when crushed (people describe it as rotten coconut, oddly specific but accurate). Neither species cares about wood structure one way or another. If an ant problem involves tunneling through a window frame or porch beam, you're dealing with carpenter ants, not the ones raiding your pantry for crumbs.

Where they show up and why it matters

Carpenter ants gravitate toward wood that's already got some moisture damage. That's why you'll often find them near leaky roof flashing, under window sills with failed caulking, around deck ledger boards, or inside a bathroom wall with an old plumbing leak nobody noticed. They don't need rotten wood to start a colony, but moisture-softened wood makes the job easier, and more often than not that's where I find the first signs during an inspection.

A satellite colony is worth knowing about too. Carpenter ants frequently set up a main colony outdoors, maybe in a dead tree stump or a woodpile, then send smaller satellite colonies into a house once they've found a good damp spot. That's part of why you might see ants indoors for weeks without finding an obvious food source. They're not necessarily nesting in your kitchen. They might just be commuting in from the backyard.

Regular household ants, by contrast, show up because of food. Plain and simple. Pavement ants and odorous house ants appear because something edible is available, whether that's a dropped cereal flake or a sticky spot behind the stove. Deal with the food source, clean the trail, and the problem often resolves faster than people expect.

Why species identification changes the price tag

This is the part that actually affects your wallet, so pay attention. A regular ant problem, pavement ants coming in under a door threshold, say, is often treatable with targeted baiting and some sealing work. A professional visit for that kind of job generally runs $150 to $300, depending on the size of the house and the company.

Carpenter ants are a different animal, pricing-wise. Treatment often needs to address both the indoor satellite colony and the outdoor parent colony, and sometimes there's more than one parent colony, which nobody loves to discover. Initial treatment costs tend to run higher, often $250 to $600, with follow-up visits sometimes needed over the following months. If there's wood damage involved, repair costs sit completely outside the pest control bill and depend on how much structural work is needed. That's something a carpenter should assess, not an exterminator.

I've always thought the identification step gets undersold by companies trying to rush through a quote. A five-minute look at the ants themselves, plus a walk around the exterior checking for frass and moisture points, tells you almost everything about what the job requires. Skip that step, and homeowners end up either overpaying for simple pavement ant bait stations or underpaying for what turns out to be a structural carpenter ant situation that needed a more thorough approach from day one.

A few common questions

Do carpenter ants actually weaken a house the way termites do? Generally not to the same degree, since they're excavating rather than consuming wood. But an established, untreated colony over several years can still cause real structural softening, especially in already moisture-damaged framing.

Can I just use store-bought ant bait on carpenter ants? Sometimes it knocks back a small trail. It rarely reaches the main colony, though, so more often than not the problem returns within weeks.

How do I tell carpenter ant frass from sawdust left by drilling or woodworking? Frass usually includes tiny insect body parts mixed in with the wood shavings, visible if you look closely with a magnifying glass. Plain sawdust won't have that.

**Is Camponotus pennsylvanicus the only carpenter ant species I'd find in Illinois?** It's the most common one in this region, though a few other Camponotus species turn up occasionally. Identification down to the exact species usually isn't necessary for treatment decisions anyway.