The thief ant is one of the smallest ants in Canada. It is named for its habit of stealing food and brood (ant larvae and pupae) from larger ants.
Why are thief ants a problem?
Thief ants are tiny and can get into sealed food packaging. Because they feed on dead mice and rats, the ants possibly may contaminate food and spread disease.
What do thief ants look like?
The thief ant is one of the smallest pest ants in Canada. It often is confused with the pharaoh ant, which is similar in size and colour. Key characteristics of the thief ant:
- Size: 1.5 to 2.2 mm or about 1/16 inch
- Colour range: yellow to light to dark brown
- Distinguishing feature: the tip or club of its antenna has two segments, while the pharaoh ant’s antennal club has three segments
What should I know about thief ants?
To get rid of thief ants, it helps to know how they live and behave:
- A thief ant colony may have one or more queens and contain hundreds to a few thousand worker ants.
- Thief ants eat seeds, ant brood and dead insects. Because they also eat dead rats and mice, thief ants may transmit disease to food.
- Outdoors, the ants build nests in exposed soil, under rocks and other objects. Thief ants may nest near the colonies of larger ants. They build tiny connecting tunnels to the other colony and use the tunnels to steal food and brood.
- In hot weather, the ants come indoors in search of water and high-protein, high-fat food, such as cooking grease, cheese, meat and oily seeds. As such, they’re often called “grease” ants. They are not attracted to sweet or sugary foods. Because of their size, thief ants can get into sealed food containers.
- Thief ants will travel long distances to find food. When they find it, the ants form a trail from nest to food and back. Following the trail will help you locate the nest. This isn’t always easy as the ants may travel behind baseboards and in walls along wires and pipes. Get tips for how to follow ant trails.
- Winged thief ants may be noticed in late summer / early fall during mating season.
Where are thief ants found indoors?
Because of their size, thief ants may go unnoticed indoors for some time. Most often they will be found foraging for water and food in kitchens, where pet food it stored and in bathrooms.
Indoors, thief ants may nest in kitchen cabinets, underneath countertops, under floors, behind baseboards and in the small crevices of woodwork and masonry.
Where are thief ants found outdoors?
Outdoors, thief ants are found in lawns, rotting wood, tree cavities, trash and along walkways and foundations. Mounds of excavated soil may indicate a thief ant nest.
How do thief ants get in the house?
Thief ants get into buildings through cracks in the foundation and concrete floors, gaps in caulk around windows and doors, and under doors without adequate seals. Read our expert guide: How to Keep Ants Out.
What are the best ant killers for thief ants?
To eliminate thief ants, use a combination of pest control products:
Ant traps – Ant traps (also known as insect bait stations) are filled with an insecticide bait. Foraging ants take bait back to the colony where it is shared among the workers, larvae (baby ants) and queen. Ant traps (also called ant bait stations) are a good choice when you have an indoor thief ant nest that is difficult to locate. Ant traps also can be used outdoors. Use a fat - or protein-based insecticide bait or mix some peanut butter and oil into the bait. Place traps near thief ant nests or trails. Learn more about ant traps, insecticide baits and how to use them.
Diatomaceous Earth – Often called DE ant powder or DE ant dust, this natural desiccant kills ants by drying them out. Apply it to indoor areas where ants are active, such as in wall voids behind electrical outlets and where plumbing and wiring enter walls. The ants walk through the DE, which scratches the waxy outer layer of their exoskeleton. This causes the ant to dry out and die. DE will not kill the colony, but it will reduce the number of foraging ants. Learn more about DE and how to apply it.
Ant repellents – Available as aerosols, foams, sprays and organic sprays, these products kill ants on contact and are most effective when applied directly to the thief ant nest. Repellent sprays also create a defensive barrier that the ants will not cross. However, if the thief ant colony has more than one queen, the indiscriminate application of repellent – while killing a few ants -- may cause the colony to panic and split into multiple nests, creating a bigger ant problem.
Also read:
5 Steps to Get Rid of Ants for Good
