Thief Ant


Actual Size: 1.5 to 2.2 mm

Characteristics: Brown to yellow in color 

Legs: 6

Antennae: Yes

Wings: No

Habitat: Builds nests in exposed soil, under rocks, or in rotting wood. Indoors, they nest in woodwork and masonry.


  • Often mistaken for Pharaoh ants.
  • Prefers greasy foods, meat, and dairy.
  • Will nest near other ants, then steal the food and larvae from their neighbor.

Thief Ants in Wisconsin

Thief ants are distributed throughout much of Wisconsin and get their name from their habit of nesting near other, larger ants. They enter their neighbor’s nest to steal food and prey upon larvae. Colonies of thief ants tend to be small but they can contain multiple queens and several thousand workers. Outdoors, these ants feed on rodents and insects. Also known as grease ants, thief ants enjoy feeding on potato chips and other greasy household foods.

Thief Ant Habitat

Outdoors, nests are found in exposed soil, under rocks, or in rotting wood. Indoors, they nest in woodwork and masonry. Thief ants enter structures through cracks in the foundation or small openings in woodwork, especially during hot weather. They use electric wires in wall voids to move from one room to another. Commonly found in kitchen areas of homes, thief ants forage in trails seeking greasy foods, proteins, and dairy products.

Thief Ant Behaviors, Threats, or Dangers

Thief ants can bite, though they rarely do. They are considered a danger as they feed on dead rats, mice, and insects. When they enter homes, thief ants may be carriers of disease-producing organisms, contaminating food sources as they forage. Thief ants trail inside cabinets, on walls, baseboards, tree branches, and shrubs. Due to their small size, they are able to forage into packaged foods. If a thief ant infestation is suspected, it is recommended to contact a licensed ant exterminator.