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Thief Ants

Also known as grease ants and sometimes "sugar ants", thief ants are one of the tiniest household ant species found worldwide. These ants are about 1/16-inch long. The name is derived from the ants' habit of stealing larvae and pupae from neighboring colonies. They are omnivorous and feed on food that is high in protein, including the larvae and pupae of other ant species, as well as other insects.

While thief ants and pharaoh ants resemble one another, several characteristics of the thief ant can ensure proper identification. The thief ant is light brown or yellow in color and measures only 1/16-inch in length. Thief ants have petioles with two nodes, one thorax without spines, ten segmented antennae with two-segment antennal clubs and small, compound eyes. The thief ant also tends to forage in well-defined trails, while Pharaoh ants are less likely to make trails but do so after food or water sources have been established.

Thief ant colonies tend to be smaller than those of other species, but can contain two or more queens and several thousand workers. The thief ant queen is capable of establishing new colonies without the help of her workers, though she may still choose to include two or more workers after mating.

Thief ants feed on protein and greasy foods such as nuts, meats, cheese, peanut butter and sweets. Because worker thief ants are small enough to enter food packaging, they can become a nuisance in the kitchen. Outside, thief ants forage for dead insects and rodents. Because of this, it is possible they can transmit pathogens from a food source to human food.

Thief ant mating swarms appear from July to September, though these reproductive ants may also be seen indoors in the summer. When thief ants enter homes and buildings, they form trails from the food source to their nests. 

Thief ants nest in rotting wood and soil. They may also nest indoors in small spaces, including wall crevices, cabinet voids, under countertops and behind baseboards. Because thief ants nest in hidden areas, their nests are difficult to locate. The best way to address a thief ant infection is to contact your local pest control professional.