Thief Ant

Description: Thief ants are very tiny ants; workers are never more than 1/16 inch long. The thorax lacks distinct spines, the petiole has two nodes and there is a small stinger at the tip of the abdomen. Thief ants are yellow to light brown and look much like Pharaoh ants. These two ants are easily distinguished because thief ants have a large two-segmented club at the tip of the antenna Pharaoh ants have a three-segmented club. Thief ants also have very small eyes.

Biology: These ants begin swarming as winged reproductives in Junes; this activity continues until late fall. A colony of a few hundred to several thousand workers can be established by a single fertilized female. Developmental time (egg to adult) is 50 days to several months.

Habits: Thief ants are often found in very large nests that have tiny tunnels connecting to the nests of larger ants. They habitually steal food and broad from the other ants’ nests; thus. their name. Thief ants usually nest outdoors in areas with bare soil or under stones. When they do nest in structures, they usually are found in wall voids and similar protected locations. Thief ants feed on live and dead insects, seeds and honeydew. They will tend aphids and other honeydew-producing insects as a source of this food. They generally prefer food with high protein content.

Control: All cracks and gaps in exterior walls which provide access to voids or interior areas should be sealed. All debris from the exterior of the structure and other items on the ground where these ants nest should be removed.

Thief ants prefer high protein foods; however, they might also respond to sweet baits. Baiting might be ineffective because these ants usually stop feeding on the bait before enough is consumed to eliminate the colony. If baits are used, they should be placed where ant trails have been established and in locations where the ants have been sited. Unless using containerized baits indoors, baits should be placed so they are inaccessible to children and pets. Protein baits are the most effective; however, if acceptance is low, a sweet bait should be considered.\The most effective control is accomplished when ant trails are followed to find and treat the nest with a residual insecticide. Exterior nests should be drenched with a liquid formulation. Nests within wall voids are more easily treated by aerosol, a barrier spray should be applied to foundations and the soil immediately adjacent to the building. This is effective in repelling foraging workers and preventing them from reentering the structure.

Controlling aphids on ornamental plants and trees around structures removes their primary food source and causes them to forage elsewhere for food.