Thief Ant Infestation

The thief ant (Solenopsis molesta) has a descriptive common name because the ants may feed their own colony members with food and ant larvae taken from other ant species’ nests. Thief ants nest outdoors in soil under rocks, fallen logs and similarly protected sites.

They will move inside a home or building when outside conditions become harsh. Inside, they nest in wall voids, cracks and crevices and other protected sites close to food sources. Thief ants establish foraging trails to their food sources and, due to their small size, are known to get into packaged foods. Indoors, they prefer foods such as oily and fatty meats, sweets and cereal products.

Outdoors, they feed on almost any organic matter like honeydew, other insects and seeds. Nest populations vary in size, and nests have multiple queens. Many experts think thief ants and pharaoh ants are among the most difficult ants to control.

Prevention & Control

• The first step in thief ant management is to positively identify the ant. Thief ants and pharaoh ants look very similar, so you should contact your pest management professional (PMP) or another expert to determine the correct species of ant causing the problems.

• Inspect your premises to locate where ant foraging trails are found. This will help locate the ant colony. If you find ants foraging from the outside to the inside, seal the openings they are using to gain access to the inside.

• Keep vegetation, mulch, landscape timbers, firewood and debris away from the structure’s foundation. These items give ants a good nesting site.

• Moisture also attracts ants, so leaky faucets and pipes, clogged gutters and downspouts should be repaired.

• Practice good sanitation to keep food sources to a minimum. Keep foods in sealed containers or put them into the refrigerator. Do not leave open foods or scraps on countertops. Do not leave pet foods out overnight. Do not let food scraps or dirty dishes sit in the sink overnight.

• Sweep and mop floors. Throw away garbage regularly and keep the trash container clean.

• Reduce and eliminate clutter.

• Removing foraging ants with a sponge will not do a lot to eliminate the colony, but it helps to temporarily reduce the number of ants crawling on your countertops or appliances.

• Do not spray ants inside the home since this is unlikely to prevent more ants from entering. Spraying ants only kills some of the members of the ant colony and will likely make ant control more difficult. Vacuuming indoor ants is better than spraying with insecticides.

• Removing food sources increases the likelihood that foraging ants will collect and take bait formulations back to the colony. Depending on baits is the right way to control the indoor ant colony.

• Both you and your PMP are crucial players in thief ant control. Your PMP is experienced and knowledgeable in selecting and using the proper baits. Also, your PMP will know the various regulatory requirements for safe and effective use of products.