Quick answer
A carpenter ant is a large ant, in the genus Camponotus, that hollows out wood to build its nest, usually wood that is damp, decayed or soft, but does not eat the wood the way termites do.
Workers are about 1/4 to 1/2 inch long. Indoor nests are often satellites of a parent colony outside, so finding and treating every nest is the key to control.
Quick facts
The key facts about Carpenter Ant, with sources:
Key takeaways
- Carpenter ants dig nests in wood but feed on sweets, insects and other foods, not wood.
- They prefer wood softened by water or decay, so a nest often points to a leak.
- Large black ants indoors in spring, coarse sawdust and rustling in walls are the signs.
- Indoor nests are usually satellites of a parent nest outdoors, often within 100 yards.
- Spraying the ants you see does not stop the colony; the nests must be found.
What a carpenter ant is and what it does to wood
Carpenter ants are some of the largest ants around homes. Penn State lists black carpenter ant workers at 1/4 to 1/2 inch and winged queens up to 3/4 inch 2. They chew out tunnels and rooms in wood to raise their young, and push the shavings out of the nest.
They do not digest wood; instead they eat honeydew from aphids and scales, live and dead insects, and household foods such as sweets and fats 41. That is the main difference from termites, which eat the wood they live in.
In forests they are helpful, and Cornell Cooperative Extension notes they prey on other insects and speed the decay of stumps and logs 4. The trouble starts when a colony moves into a house, usually where water has softened wood.
A carpenter ant cannot sting, but UC IPM says it can bite and spray formic acid into the wound 1.
How a carpenter ant colony grows into a house
- A queen starts alone: After a spring mating flight, she seals herself in a small chamber in wood and lays eggs 4.
- A small first brood: Penn State says the first brood is 15 to 20 eggs; egg to worker takes at least about 60 days 2.
- Years of growth: Colonies grow to 2,000–4,000 ants and start making swarmers at about 3.5 to 4 years old 3.
- Satellite nests: The parent nest, often in a stump, tree or woodpile, sends workers and brood to satellite nests, including inside walls 1. Penn State says the parent may be within 100 yards of the house 2.
- Night foraging: Workers forage mostly after sunset and may travel up to 100 feet from the nest 3.
- Swarm: Each summer, 200 to 400 winged ants develop, overwinter in the nest and fly out the next spring or early summer 2.
- Wall-void satelliteOlder larvae, pupae and workers
- Hollow door or window frameDamp, soft wood
- Foam insulation boardSoft material easy to dig
- Porch or deck timberWood exposed to water
Both parent and satellite nests must be found, or ants return within days or weeks. Source: [1] [2]
Common carpenter ant species
| Species | Where | Look | Notes |
|---|---|---|---|
| Black carpenter ant (Camponotus pennsylvanicus) | Eastern U.S.; most common in Ohio and Pennsylvania 32 | Black; workers 1/4–1/2 inch 2 | Mature colonies of 2,000–4,000 3 |
| C. noveboracensis and C. nearcticus | New York State 4 | Varied; some partly red 4 | Listed by Cornell as destructive wood pests 4 |
| Camponotus modoc | Western U.S., including California 1 | Black with dark red legs; 1/4–1/2 inch 1 | Swarms late afternoon, often after heavy rain 1 |
| Camponotus vicinus | Western U.S., including California 1 | Usually red and black 1 | One nest can hold up to 40 queens 1 |
| Camponotus clarithorax | California 1 | Yellow and black, about 1/8 to under 5/16 inch 1 | Smaller than the two above |
Carpenter ants have one node (bump) in the waist and an evenly rounded back seen from the side 1. Our pest identifier helps separate them from other large ants.
Example: tracing ants back from the kitchen
This example shows how the published biology guides a search. The scene is an illustration; the figures are from the sources.
| Clue | Published fact | What to do with it |
|---|---|---|
| A few large black ants in the kitchen in May | Large, wingless, dark ants indoors are usually the first sign 2 | Treat as a possible nest, not stray visitors |
| You see more at night than by day | Activity peaks after sunset; Penn State suggests checking between 10 p.m. and 2 a.m. 23 | Follow trails with a flashlight at night |
| Trail leads out under the back door | Foragers travel up to 100 feet from the nest 3 | Search the yard, stumps and woodpiles |
| Winged ants at an inside window in spring | Winged ants indoors suggest an indoor nest 2 | Look for a satellite nest in walls or frames |
| Coarse sawdust under a window frame | Frass looks like pencil-sharpener shavings 3 | Mark the spot; check for moisture |
The ants in your kitchen are only foragers, since only about 10% of a colony forages at any time 1, so the real work is finding the nests.
Where the term shows up on reports and quotes
On a wood-destroying organism inspection, an inspector may note carpenter ants, frass or ant damage alongside termite findings; ask whether your state’s form covers them. The report may also note moisture problems that drew them.
On a service quote, look for how the company plans to find the parent and satellite nests, which areas it will treat, and how many visits are included. A quote that only offers a perimeter spray may leave nests untouched.
On a general ant control plan, ask whether carpenter ants are included or quoted separately, since finding nests in walls takes extra time.
Warning signs of carpenter ants
- Large, wingless, dark ants indoors, especially in spring and at night 2.
- Coarse, stringy sawdust piles near cracks, moldings and porches 2. The frass may hold insect parts and seed husks 3.
- A dry rustling sound in walls, like crinkling cellophane 3.
- Winged ants at indoor windows in spring 2.
- Smooth, clean tunnels in wood with no soil or droppings 2.
- Damp or decayed wood near kitchens, bathrooms, porches or roofs 4.
Dusts and sprays need care
Do not drill into walls or blow dusts around wiring without training. UC IPM warns that desiccant dusts can seriously irritate the lungs, and some products are for licensed applicators only 1. Follow every label. Anyone exposed to an ant spray or dust should call Poison Help at 1-800-222-1222.
What each control approach does well
Strengths
- Moisture repair removes what drew them: fixing leaks, gutters and ventilation 1.
- Slow-acting baits are carried back to the nest and shared, and the label must list ants 1.
- Direct nest treatment with labeled dusts or sprays works when the nest is found 12.
- Removing outdoor nests with the infested stump or wood cuts off the source 2.
How much damage carpenter ants really do
Damage is usually slower and smaller than termite damage. Penn State says structural damage from carpenter ants is rare and that they seldom tunnel into dry, sound wood 2.
Damage can still add up, because UC IPM notes that a large colony’s network of galleries can compromise structural integrity, and they nest in wall voids, hollow doors and insulation 1. Cornell points to porches, roofing and areas near kitchens and bathrooms where water collects 4.
The bigger warning is often the water, since a nest in a wall usually means wood has stayed wet, and that wood may also be rotting.
What drives the cost of carpenter ant control
We do not quote prices here. The cost drivers are how many nests there are, how hard they are to reach and how many visits it takes.
A job with a nest in an outdoor stump costs less effort than one with satellites inside finished walls. Drilling and treating voids, follow-up visits and any carpentry to replace wet or damaged wood all add up. Fixing the leak is often the biggest single item, and it is not pest work.
Ask how long the service is guaranteed and whether return visits are included. Our pest control cost guide explains how quotes are built, and the recurring plan tool compares one-time and ongoing service.
How a professional carpenter ant job usually runs
- Inspect at the right time: UC IPM says after sunset is the best time to find trails 1.
- Find the nests: Follow trails, listen for rustling, look for frass and probe damp wood 3.
- Treat the nests: Labeled dusts or sprays go into nest galleries or voids; drilling may be needed 12.
- Bait where needed: Slow-acting baits along trails reach nests that cannot be found 1.
- Fix the cause: Repair leaks and replace decayed wood 1.
- Follow up: Baits may need repeat visits by a professional 2.
Our ant control service page explains what a visit includes. Satellite colonies usually need professional treatment, Penn State says 2.
Making a house less attractive to carpenter ants
- Trim tree branches and shrubs so they do not touch the house 1.
- Keep mulch near the foundation to 2 to 3 inches deep 1.
- Store firewood off the ground and away from the house 12.
- Fix roofs, flashing, gutters and downspouts so wood stays dry 2.
- Seal openings where utility lines enter 1.
- Remove stumps and waste wood near the house where practical 23.
- Cover crawl space soil with a plastic moisture barrier and ventilate it 2.
Dry wood is the best defense
Penn State says carpenter ants usually will not infest sound wood with a moisture content below 15 percent 2. Keeping wood dry protects it from ants and rot at once.
Our page on moisture control for pest prevention covers the water side in more depth.
When to call a professional
Call when you see frass, hear rustling in walls, find winged ants indoors or keep seeing large ants inside after you have cleaned up food.
Call when nests are inside walls, ceilings or other places you cannot reach. Penn State notes satellite colonies usually need professional treatment 2.
Call a contractor too if you find soft, wet or damaged structural wood.
Rules and standards that apply
Federal (EPA, FIFRA): Every insecticide must be EPA-registered and used as the label says. UC IPM notes the label of a bait must list ants as a target pest 1.
Restricted products: In California, UC IPM says silica gel and fipronil perimeter sprays can only be applied by a licensed applicator 1, and the rules differ in other states.
State licensing: Pest control companies and applicators are licensed by the state. See pest control licensing and our pesticide safety guide.
Carpenter ant vs termite
| Feature | Carpenter ant | Subterranean termite |
|---|---|---|
| Eats wood? | No; digs nests 1 | Yes 5 |
| Gallery contents | Clean, sanded look; no soil 34 | Soil in galleries |
| Debris | Coarse sawdust pushed out 2 | Mud tubes 5 |
| Waist and antennae | Pinched waist; elbowed antennae 5 | Broad waist; straight antennae 5 |
| Wings | Front wings longer 5; not shed quickly 3 | Equal length; shed soon 5 |
| Seen outside the nest? | Often, foraging at night 3 | Seldom 4 |
See our pages on the subterranean termite and termite swarmers for the termite side.
Common carpenter ant myths
How species and timing differ by region
Which carpenter ant you have depends on region. In the East and Midwest, the black carpenter ant is most common; Ohio State says swarmers usually emerge from March to July 3, and Cornell notes outdoor activity in New York mostly runs from May through September 4.
In the West, UC IPM lists C. modoc and C. vicinus as the most destructive species, and C. modoc swarms in late afternoon after heavy rain 1. Homes in wooded areas are especially prone 2.
In heated buildings, activity can start earlier and run later than outdoors 4.
When it matters to you, and what to do next
A few large ants outside are normal, but when you find large ants inside in late winter or spring, or see frass or winged ants indoors, a nest is likely in the house, so look for the moisture source and book an inspection.
Before hiring, ask how the company will find the parent and satellite nests and how it will fix the moisture problem. Our guide to choosing a pest control company lists more questions.
Quick decision guide
Ants only outdoors call for prevention. Ants indoors in spring are worth tracing at night. Frass, rustling or winged ants inside call for an inspection and a moisture check.
Questions about Carpenter Ant
How do I know if I have carpenter ants or termites?
Look at the debris and the insect, because carpenter ants push out coarse, stringy sawdust and leave clean tunnels with no soil; subterranean termites leave mud tubes and soil in their galleries.
Ants have a pinched waist and elbowed antennae; termites have a broad waist and straight antennae. A sample in a sealed bag helps a pro confirm.
Do carpenter ants eat wood?
No, carpenter ants do not eat wood. UC IPM and Ohio State Extension both say they dig wood out to make nests and discard the shavings. They feed on honeydew from aphids and scales, other insects and household foods such as sweets and fats. Termites, by contrast, eat and digest the wood they live in.
What does carpenter ant sawdust look like?
Carpenter ant sawdust, called frass, looks like coarse, stringy pencil-sharpener shavings. Ohio State notes it may contain insect parts and seed husks. It piles up below small openings, often near cracks, moldings and porches. Drywood termite droppings are different: hard, six-sided pellets of even size.
Why do I see carpenter ants in spring?
Spring is when carpenter ants become active and swarm. Penn State says winged ants that developed the summer before leave the nest in spring or early summer. Penn State adds that large, wingless, dark ants indoors are usually the first sign, and winged ants at indoor windows suggest an indoor nest.
Where do carpenter ants nest in a house?
Carpenter ants nest in damp or soft wood and other soft materials. UC IPM lists wall voids, hollow doors and insulation. Cornell names porches, roofing and areas near kitchens and bathrooms where water collects, and Penn State adds foam insulation board. Many indoor nests are satellites of a parent nest outdoors.
How big do carpenter ant colonies get?
A mature black carpenter ant colony usually holds about 2,000 to 4,000 ants, according to Ohio State Extension.
Penn State puts the point where a colony starts making swarmers at roughly 2,000 to 3,000 workers.
UC IPM says indoor satellite nests can hold several thousand ants, and one western species can have up to 40 queens.
Can carpenter ants bite or sting?
Carpenter ants cannot sting, but they can bite. UC IPM says they may also spray formic acid into the wound, which causes a burning feeling. Bites are rare and usually happen when ants are handled or a nest is disturbed. Seek medical care if a bite looks infected or you have a strong reaction.
Will ant spray get rid of carpenter ants?
Spray alone usually will not get rid of carpenter ants. Ohio State says the queen must be killed, and killing foragers is not enough. Penn State notes sprays, dusts and baits give only partial control unless the parent and satellite nests are found. Slow-acting baits that list ants on the label can reach hidden nests.
Do carpenter ants cause serious damage?
Carpenter ants can weaken wood over time, but serious structural damage is uncommon. Penn State says damage from nest expansion into timbers is rare, and they seldom tunnel into dry, sound wood.
UC IPM notes that a large colony’s galleries can compromise structural integrity. The moisture that drew them may cause more harm than the ants.
Sources
- UC Statewide IPM Program, Pest Notes: Carpenter Ants (Publication 7416), retrieved .
- Penn State Extension, Carpenter Ants, retrieved .
- Ohio State University Extension, Carpenter Ants (HYG-2063), retrieved .
- Cornell Cooperative Extension, Suffolk County, Carpenter Ants (hosted by Maine DACF), retrieved .
- U.S. EPA, Termites: How to Identify and Control Them, retrieved .
Expert review
Written by the HyrePest Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Size, colony, nesting, signs and control facts follow UC IPM Pest Notes 7416, Penn State Extension, Ohio State HYG-2063 and Cornell Cooperative Extension, attributed to each. Ant-versus-termite features are from the EPA.
Suggest a correction. We fix errors and say what changed.