Small Ants in Your House: How to Identify Them and Get Rid of Them for Good

TL;DR

• Small ants in your house are workers looking for food and water. Many come from a nest outside or inside a wall.
• In Canada they are often little black ants, pavement ants, odorous house ants, thief ants or pharaoh ants, and the species decides which bait works.
• Use a slow-acting bait that workers carry back to the nest. Don't spray: it usually kills only the foragers, and UC IPM warns that sprays can scatter the colony to new locations.
• Match the bait: odorous house ants prefer sugar, according to Penn State Extension, and many pavement ants go for it too, while thief and pharaoh ants prefer protein or greasy baits (UC IPM). Not sure? Set both side by side.
• Put several bait stations on or near the active trails, as UC IPM advises, and keep baits out, often for two weeks or more. Seeing more ants at first usually means they found the bait.
• Need help? Get a quote from a recommended local exterminator through Pest Agent's referral form.

Small ants in your house tend to appear all at once: an empty counter one evening, a busy line along the backsplash the next morning. Most of them likely have not moved in, at least not yet. They are usually foragers walking in from a nest outside or tucked inside a wall.

Several tiny species invade Canadian homes, and to the naked eye most look like the same brown or black speck. They differ in what they eat, where they nest and how they react to a can of spray, and UC IPM warns that sprays can disperse some colonies to new locations, so a product that clears one species may push another to split into new nests. What they share is the reason they came indoors in the first place.

Why Are There Small Ants in Your House?

Small ants in your house are worker ants looking for food and water, and most of them come from a nest outside or inside a wall. The City of Calgary notes that there are many species of ants in Canada and that most nest outside and usually come into buildings only to forage. One scout finds a crumb, lays a scent trail, and the rest of the workers often follow it to the same spot.

Food

Food is the main reason small ants come inside. Depending on the species, they go after sweets, grease, meat, crumbs, pet food and dead insects. A sticky spill on the counter, an open bag of cereal or a full pet bowl is enough to start a trail.

Water

Water draws ants to sinks, bathtubs, the cabinet under the sink and any leaky pipe or tap. Several small household ants, including odorous house ants, often nest near moisture and warmth, such as wall voids around water pipes.

Shelter

Shelter matters too. Some small ants nest right inside your walls, under carpets, in woodwork and behind baseboards. Pharaoh ants go further: in a cold climate like Canada's, they generally live only in heated buildings, so they can stay active all year.

Seasons

Seasons change what you see. Pavement ants, for example, often cause the most problems indoors in spring and early summer, according to Utah State University Extension. Ants that already nest indoors, like pharaoh ants, can show up in the middle of winter.

What Kind of Small Ants Are in Your House?

Small ants in your house in Canada are usually little black ants, pavement ants, odorous house ants, thief ants or pharaoh ants, and the species decides which bait works. Health Canada lists all of these among the ants that invade homes. The smallest, little black ants and thief ants, are only about 1 mm long. A magnifying glass and a good look at the colour, the waist and the antennae will usually narrow it down.

Little Black Ants

Little black ants (Monomorium minimum) are tiny, shiny black ants, about 1.5 to 2 mm (about 1/16 inch) long, and the workers are usually all the same size. Their antennae usually have 12 segments ending in a club of 3 segments. They are a native species found from southeastern Canada into the United States. A colony can hold a large number of workers and many queens (Texas A&M AgriLife). Outdoors, they nest in lawns and under stones, bricks and wood. Indoors, they nest in wall voids, woodwork, masonry and under carpets, and they are easy to spot on their trails into food cabinets and pantries. They eat grease, oil, meat, fruit, vegetables and sweets.

Pavement Ants

Pavement ants are dark brown ants, about 2.5 to 3 mm long, with fine parallel grooves on the head and thorax and a waist with two nodes (Utah State University Extension). They nest in soil under rocks and pavers, along curbs and in cracks in pavement and foundations, often with a small volcano-shaped pile of dirt at the entrance. Indoors, they follow baseboards, carpet edges and pipes, and come in through foundation cracks, door and window frames and heating ducts. They eat sweet and greasy foods, seeds, dead insects and pet food.

Odorous House Ants

Odorous house ants are brown to black, about 2.4 to 3.3 mm long, and can give off a rotten coconut smell when you crush one (Penn State Extension). Their single waist node is hidden under the abdomen. They love sweets, so sweet baits are the usual choice. Our full guide to odorous house ants covers them in detail.

Thief Ants

Thief ants are among the tiniest ants in Canadian homes: yellow to light brown, about 1/32 inch long, with very small eyes (UC IPM). Their antennae usually end in a club of 2 segments, which helps separate them from pharaoh ants. Thief ants prefer greasy and protein foods over sugar, are small enough to get into packaged food, and travel along electrical wires, so you may see them coming out of outlets.

Pharaoh Ants

Pharaoh ants are typically about 1.5 to 2 mm long, yellow or light brown to reddish, often with a darker abdomen (UF/IFAS). In Canada, they generally live only inside heated buildings. They are the one small ant you should never spray: Alberta Health Services warns that sprays can make the colony bud, or split into several new nests, and UC IPM says sprays only make infestations worse. If your tiny ants are pale and show up in several rooms, read our guide to pharaoh ants before you treat.

Are They Sugar Ants?

"Sugar ant" is not one species in Canada. It is a loose name people use for small ants that go after sweets, and it gets applied to pavement ants, odorous house ants, pharaoh ants and little black ants alike. If you call them sugar ants, our guide on how to get rid of sugar ants walks you through the sweet-bait approach.

Is It a Carpenter Ant?

A carpenter ant is not a small ant: Health Canada puts carpenter ants at up to 13 mm, much bigger than the tiny ants above. Carpenter ants nest in damp or decaying wood and can damage it, and piles of sawdust are a typical sign. If you see large black ants or sawdust, check the signs of carpenter ants in your house instead.

Are Small Ants Harmful?

Small ants are mostly a nuisance, not a danger. Health Canada notes that most common Canadian ants are not aggressive. The real concern is food: Penn State Extension notes that their feeding can contaminate stored pantry items. Pharaoh ants are the exception worth taking seriously, because they can carry germs such as Salmonella and Staphylococcus (UF/IFAS). Throw out any food the ants have reached.

How Do You Get Rid of Small Ants?

Getting rid of small ants usually works best with a slow-acting bait that worker ants carry back to the nest, matched to the food your species prefers. The ants you see are only a small part of the colony. The goal is to reach the queens, and only the workers can take the bait to them.

Why Sprays Make Small Ants Worse

Sprays make small ants worse because they kill only the foragers and can scatter the colony. Health Canada advises switching to a bait system if indoor spraying seems to increase the number of ants, and says not to spray ants while you are using baits, because it stops the baits from working. The City of Calgary warns that some barrier sprays can make the colony bud, and with pharaoh ants it is a well-known problem. UC IPM adds that indoor sprays usually are not needed and may not stop new ants from coming in.

Follow the Trail

Following the trail tells you where to put the bait and where the ants come in. Watch the line of ants for a few minutes: trails usually run along baseboards, carpet edges, cabinet corners, pipes and wires, and they lead back toward the nest or the gap the ants use to get inside.

Finding the Nest

Finding the nest tells you whether the problem starts outside or in your walls. According to the Northeastern IPM Center, several workers without wings often point to a nest outdoors nearby, while winged ants inside the house may suggest a nest indoors. Outdoor nests are often under stones, pavers or a small mound of soil near the foundation.

Sweet Versus Protein Baits

Sweet versus protein baits is the most important choice you make. Penn State Extension notes that odorous house ants prefer food high in sugars, and many pavement ants go for sugar too, while thief ants and pharaoh ants usually prefer protein or greasy baits all year, according to UC IPM. If you are not sure, put a small amount of each type side by side and use the one the ants eat. Health Canada also suggests using two different baits at the same time. For tested products sold in Canada, see our picks for the best ant killer.

Bait Placement

Bait placement decides whether the bait reaches the colony. Put bait stations or small dots of gel right on the active trails, along baseboards, carpet edges and cabinet corners, and use several stations rather than one. Remove other food sources so the bait is the easiest meal around. Keep every bait out of reach of children and pets, and check that the label lists your type of ant and shows a PCP number, which means Health Canada has approved the product. If you have pets, read our guide to pet-safe ant killers.

How Long Baiting Takes

Baiting small ants takes days to weeks, not hours. You may see more ants at first, which means they found the bait. UC IPM says to expect about 5 to 10 days before numbers drop and often several weeks for full control, and Health Canada says to keep baits out for at least two weeks and reapply as needed. Replace empty baits, and move or switch them if the ants ignore them.

Homemade Borax Bait

Borax baits can work on sweet-loving small ants because borax, like boric acid, acts slowly enough for workers to share it, but Health Canada advises Canadians not to make homemade pesticides using boric acid, and borax can produce boric acid. Health Canada notes that boric acid baits are generally low in toxicity to other animals, but they still have to be kept away from children and pets. Our guides on using borax to kill ants and homemade ant killers explain the registered options and where to place them.

Diatomaceous Earth

Diatomaceous earth is a non-chemical dust made of crushed marine fossils that dries ants out as they walk through it. Health Canada recommends putting it in cracks and crevices, notes that it works only while dry, and says it is non-toxic to people and pets, though you should avoid breathing the dust. Do not use it on the same trail as your bait: the Northeastern IPM Center advises against combining dusts like this with baits.

Outdoor Nests

Outdoor nests near your foundation can be dealt with directly. Health Canada suggests flooding the nest repeatedly with a garden hose, or pouring boiling water with detergent down the nest to temporarily reduce the colony. If you use an ant product outside, check that the label allows outdoor use and check your city or province's pesticide rules. For more, see our guide to getting rid of ants indoors and outdoors.

When to Call a Pest Control Professional

Calling a pest control professional makes sense when the ants are nesting inside your walls, when large numbers keep showing up in the same area for weeks despite baiting, or when you suspect pharaoh ants or carpenter ants. A licensed professional can identify the species, find the nests and treat them directly, which is hard to do yourself when the nest is in a wall void. You can get a quote from a recommended local exterminator through Pest Agent's referral form.

How Do You Keep Tiny Ants Out of Your House?

Keeping tiny ants out of your house comes down to removing the food and water that draw them and closing the gaps they walk through. These habits also make baits work better, because the bait becomes the easiest food available.

Food Storage

Food storage is your first line of defence. Health Canada suggests glass jars with rubber gaskets or plastic containers with tight-snapping lids for sugar, cereal and snacks. Keep counters clean, sweep or vacuum often, rinse containers before they go into the recycling, empty the kitchen garbage often and keep the composter away from the house.

Pet Dishes

Pet dishes are a favourite target for small ants. Sweep around them every day, pick up food your pet does not finish, and try Health Canada's simple trick: set the pet dish in a shallow dish of water, since ants cannot swim across it.

Moisture Control

Moisture control removes the water ants need. Fix leaky taps and pipes, wipe sinks and tubs dry at night, and do not leave damp sponges or cloths on the counter.

Sealing Cracks

Sealing cracks cuts off the paths ants use. Caulk gaps in the foundation and exterior walls, and indoors along baseboards and around pipes and wires, which ants use as highways. Duct tape or petroleum jelly makes a quick temporary seal. Ideally, seal after the bait has done its job, so you do not cut the ants off from the bait halfway through.

Plants Near the Foundation

Plants near the foundation give ants a bridge into the house. UC IPM recommends keeping plants, grass and mulch at least a foot (about 30 cm) away from the foundation, and trimming branches that touch the walls.