Thief ant—Solenopsis molesta Subfamily: Myrmicinae

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	Identifying characteristics Workers are all the same size, tiny, 1/32-inch long Yellow to light brown with very small eyes Petiole with 2 nodes Thorax uneven in shape when viewed from the side with no spines 10-segmented antennae with a 2-segmented club
Behavior Feed on grease and greasy foods, proteins, dead insects, and even dead rodents; may sometimes feed on sweets Often steal food and ant larvae from nests of other ants Travel in set trails inside cabinets, on walls, along baseboards, and along branches of trees and shrubs May travel from one room to another by traveling on electrical wires; may be seen in electrical outlets. Small enough to forage into packaged foods		Nest type and size Nest outdoors in soil under rocks or in decaying wood Indoors, colonies found in cabinet or wall voids or behind baseboards Individual colonies small; may have multiple queens

Thief Ant

Order/Family: Hymenoptera/Formicidae

Scientific Name: Solenopsis molesta (Say)

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 o 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 June; this activity continues until late fall. A colony of 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 brood 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 or 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. Protein baits are the most effective; however, if acceptance is low, a sweet bait should be considered. In areas where workers are observed the ready-to-use ant baits (syrups or solid pellets in a small canister) can be placed on or along trails, being careful to exclude contact with the bait by children and pets.

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.  When nests can not be located, 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.

Copyright © 2001 [Alan Luke]. All rights reserved.
Revised: 10/15/11. Home