Ants in the House: How to Get Rid of Them, and When It's Carpenter Ants or Termites

A line of small ants on the kitchen counter usually means one ant found food and the rest are following. Penn State Extension explains that nuisance ants follow a chemical trail to food a nestmate found, and that their nests are usually outdoors in the ground. UC IPM, the University of California's pest management program, and Penn State both recommend cleaning up the trail and the food, sealing the way in, and using slow-acting baits rather than sprays. Large black ants with coarse sawdust, or winged insects swarming indoors, can mean carpenter ants or termites, which point to moisture or wood damage and a pest management professional.

If you've found soft, crumbling wood but no insects, start with our wood rot guide. For pest-proofing the whole house each season, see the summer maintenance guide.

Why Ants Come Inside

UC IPM says ants come indoors for food and water, warmth and shelter, or relief from hot, dry weather or flooding, and can show up suddenly when the weather changes. Check these in order:

1. Food. UC IPM lists sugar, syrup, honey, fruit juice, fats, and meat among what household ants feed on. Check counters, the pantry, pet bowls, and the trash.
2. Water. UC IPM says leaky faucets and sprinkler heads attract thirsty ants. Check under sinks and around the dishwasher.
3. An easy way in. Ants trail along wires and pipes to get inside (UC IPM), and branches touching the house give them a bridge (University of Minnesota Extension).
4. A nest indoors. The University of Minnesota says some species nest in wall voids or behind baseboards and countertops, others in moisture-damaged wood, and that winged ants swarming inside indicate an indoor nest.

Identify Them

The University of Minnesota Extension calls identification the first step, because species nest, feed, and respond to treatment differently. NPIC suggests your county Extension office for help.

Small Nuisance Ants

The University of Minnesota describes two common ones. The odorous house ant is brown and about 1/10 inch long, and when crushed gives off a smell some people compare to rotten coconuts or blue cheese. The pavement ant, about 1/8 inch, nests under sidewalks and slab foundations and comes in through cracks in the concrete. Most ants are mainly a nuisance, it says. The exception is the tiny (about 1/16 inch), yellow-to-red Pharaoh ant, which nests only indoors in the north central states; the Extension highly recommends a pest management service for it.

Carpenter Ants

UC IPM and Penn State put workers at 1/4 to 1/2 inch, and the University of Minnesota says they're black or red and black, with one node at the waist and an evenly rounded back seen from the side. They don't eat wood: UC IPM says they hollow it out to nest, and Purdue Extension calls a small pile of coarse sawdust below the nest their trademark.

They're a moisture warning. Purdue says their nests are usually in wood with a “higher than normal” moisture condition, and Penn State says they usually won't infest sound wood under 15 percent moisture. The University of Minnesota lists indoor nest sites in wood dampened by leaks or condensation: behind bathroom tile, around tubs, sinks, and dishwashers, in attic beams, and in hollow doors and wall voids. Ants you see inside may be foraging from an outdoor nest (Penn State), but the Extension's signs of an indoor nest are coarse sawdust, 20 or more workers seen again and again, many winged ants indoors from late winter through spring, and carpenter ants active inside in winter. Damage usually builds over years, it says, but severe damage can weaken structural wood.

Termite Swarmers

UC IPM says winged termites are easily confused with flying ants. UC IPM, the University of Minnesota, the EPA, and Penn State describe three differences:

• Waist: narrow and pinched on an ant; broad, with no waist, on a termite.
• Wings: an ant's front wings are longer than its hind wings; a termite's four are about equal, and much longer than its body (University of Minnesota).
• Antennae: elbowed on an ant; straight on a termite.

Both shed their wings soon after flying, and the University of Minnesota says termite wings are usually found near where the termites emerged. UC IPM calls mud tubes (shelter tubes), which can run up a foundation, the most commonly seen sign of subterranean termites, and says damaged wood is often thin at the surface and easy to puncture with a screwdriver.

What You Can Do Yourself

These steps are for small nuisance ants. For carpenter ants or termites, go to When to Call a Pro.

Step 1: Clean Up the Trail and the Food

Wipe the trail with soapy water to remove the scent the others follow (UC IPM, NPIC), and vacuum up stragglers, emptying the bag outdoors right away (NPIC). Then remove the attraction: UC IPM says to keep sugar, syrup, honey, and pet food in closed containers, not plastic bags or open packages, rinse soda cans, clean up grease and spills, and take garbage out daily. As for the bug spray under the sink, UC IPM says, “Indoor sprays aren't usually necessary.”

Step 2: Find and Seal Entry Points

Follow the trail to where it comes in. UC IPM says to check under sinks, in cupboards, and along pipes and wires, then caulk the gap, or plug it with petroleum jelly. Penn State adds cracks around windows and doors. The University of Minnesota cautions that sealing isn't always practical with ants this small, which is why baits matter.

Step 3: Use Baits, Not Sprays

The University of Minnesota says killing foragers does little, since only a small share of the colony is out of the nest at any time. UC IPM explains that workers carry bait back and share it mouth to mouth with other workers, larvae, and queens, so it has to be slow-acting.

• Pick the right product. Penn State recommends enclosed, tamper-resistant bait stations indoors. The label should list ants as a target pest (UC IPM) and the place you'll use it (University of Minnesota). UC IPM warns that some granules that look like bait are contact insecticides that won't control the colony.
• Place it where they travel. UC IPM says to bait mainly outdoors, along trails and every 10 to 20 feet around the foundation, to draw ants out, and to bait indoors only for a serious infestation whose entry point you can't find. The University of Minnesota calls bait the best way to treat an indoor nest. Keep every station out of reach of children and pets.
• Leave it alone. UC IPM and the University of Minnesota both say not to spray while baiting, and the University of Minnesota says ants avoid bait contaminated by a pesticide or household chemical.
• Adjust. UC IPM says to replace empty baits and, if ants ignore one, move it or try another product; it notes that some species prefer sweet baits and others protein or grease.
• Wait. UC IPM says 5 to 10 days to see fewer ants; the University of Minnesota says weeks to months to eliminate a colony.

Why Sprays Backfire

The University of Minnesota says spraying is temporary and has little to no effect on the nest. UC IPM says perimeter sprays kill only foragers and can sometimes trap ants indoors, and for Pharaoh ants, “Insecticide sprays will only make infestations worse by dispersing colonies to new locations.” Penn State says to avoid sprays, bug bombs, and liquid concentrates indoors, since they can irritate lungs, leave residues, and be touched or swallowed by children. Home remedies don't work either: the University of Minnesota lists flooding nests, cinnamon, red pepper, orange peels, essential oils, and gasoline, which it calls dangerous.

When to Call a Pro

• Signs of carpenter ants. The University of Minnesota says control is complex and best left to a pest management professional, who may drill small holes to dust a nest inside a wall, a job it says not to do yourself. Tell the pro when, where, and how many ants you've seen. The Extension also says to replace damaged wood and fix the moisture; that's work for a carpenter or contractor (see wood rot).
• Possible termites: swarmers, mud tubes, or wood with hollow spots when probed. UC IPM says to call a professional, since do-it-yourself termite pesticides are generally not effective. The EPA says termite companies must be licensed by your state, so ask to see the license, and ask when you can go back inside after treatment. NPIC suggests getting inspections and estimates from more than one company.
• Tiny yellowish ants nesting indoors, possibly Pharaoh ants; the University of Minnesota says store baits generally don't work on them.
• Ants that keep coming back after weeks of baiting. UC IPM recommends a pro trained in integrated pest management who uses baits and spot treatments rather than perimeter or monthly sprays. The EPA says to ask them to correct the source of the problem first, and to write down the name and EPA registration number of any product they use.
• A slab house with a serious ant problem. Purdue says ants nesting under the slab may need professional control.

Prevent It

• Fix the water. Repair leaky pipes and faucets (NPIC, UC IPM) and the roof, flashing, gutter, and downspout problems that keep wood damp (Penn State), and insulate pipes that sweat (NPIC). Penn State says ants nest in clogged gutters; see cleaning gutters from the ground. The EPA says to keep the soil around the foundation dry with good grading and working gutters and downspouts; see negative grading and downspouts draining near the foundation. Penn State also recommends a plastic moisture barrier over crawl space soil; see crawl space vapor barrier.
• Seal the gaps where plumbing, cable, and electrical lines enter (NPIC, Penn State).
• Trim plants back so branches and shrubs don't touch the house, roof, or eaves (University of Minnesota, NPIC). Keep plants and mulch back from the foundation: Penn State says at least 6 inches, UC IPM at least a foot, and the EPA at least 18 inches. UC IPM says to keep mulch 2 to 3 inches deep.
• Store firewood at least 3 feet from the house and off the ground, and bring in only a couple of days' supply (Purdue). Purdue says firewood shouldn't be treated with insecticides, citing possible harmful fumes when it burns. Remove stumps and old logs near the house (University of Minnesota, Penn State, NPIC).
• Keep exterior wood painted and sealed, and replace water-damaged wood (Penn State).
• Get ahead of the season. UC IPM says to caulk and bait before the yearly invasion, and that baiting in late winter and early spring works best.

Frequently Asked Questions

Why are there suddenly ants in my kitchen?

Usually food, water, or weather. UC IPM says ants come in for food and water or to escape hot, dry weather or flooding, and can appear suddenly when conditions change. Wipe the trail, seal the food, and find where they're getting in.

How long do ant baits take to work?

UC IPM says 5 to 10 days to see fewer ants, and the University of Minnesota says weeks to months to eliminate a colony. Keep bait stocked, keep sprays away from it, and switch products if ants ignore it.

Do vinegar, cinnamon, or essential oils get rid of ants?

Not for good. The University of Minnesota says a mild vinegar-and-water wipe temporarily disrupts a trail, but it lists cinnamon, red pepper, orange peels, and essential oils among methods that aren't effective.

Are flying ants in the house a sign of termites?

Not necessarily; check the waist, wings, and antennae. Winged ants swarming indoors indicate an indoor ant nest, the University of Minnesota says. If they're termites, UC IPM says a licensed professional's inspection is usually needed to confirm an infestation.

The Bottom Line

Wipe the trail, put food away, seal the gap, and use slow-acting baits instead of sprays, following the label exactly and keeping baits away from children and pets. Big black ants with sawdust, or winged swarmers and mud tubes, point to moisture or wood damage: call a pest management professional and fix the water.

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