Facts, Identification & Control
One of the smallest ants, thief ants measure about 1.5 to 2.2 mm long. Their antennae have 10 segments with a two segmented club. They range in color from yellowish to brown.
Behavior, Diet & Habits
Thief ant nests occur in a great variety of locations outside, especially under rocks. They also may nest indoors in cracks and cupboards.
Thief ants feed on immature forms of other ants and insects. They also are attracted to greasy or high-protein foods, such as cheese and animal matter.
Queens lay eggs, which incubate and take 50 days to a few months to fully develop into adults.
Signs of a Thief Ant Infestation
Thief ant workers are the most likely sign.
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 1.5 to 2.2 mm 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. Thief ants have 10 segmented antennae ending with a two-segmented club. Pharaoh ants have 12 segmented antennae ending with a three-segmented club. 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. The thief ant is light brown or yellow in color and measures only 1.5 to 2.2 mm in length. Thief ants have a waist with two nodes, a thorax without spines and small, compound eyes.
Thief ant colonies tend to be smaller than those of other species, but can contain two or more queens and several thousand workers.
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 June to September, and 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 infestation is to contact your local pest control professional, who can identify the species properly and recommend an appropriate treatment.