NPIPM:Solenopsis molesta
Authors: Ashley Mueller, Buyung Hadi
Ants are one of the most common pests that can be found in and around homes. Ants are social insects, and they live together in colonies. They are divided into three classes called castes: queens, males, and workers. Each caste serves the colony in specific way. Queens lay eggs and care for the brood; males play a vital role in reproduction; and workers provide food to the colony by foraging. Ants use pheromones to create invisible odor trails. The workers follow the odor trails to and from the nest while foraging for food. Indoors, ants are often seen following trails.
Although ants can be a nuisance, they can also contaminate food, wreak havoc on yards, and cause structural damage to buildings. There are many ways homeowners can prevent ants from coming indoors. Identifying problematic ants is essential in determining how an infestation is managed.
Identification
Thief ants, also known as grease ants, are native to the U.S. and are one of the smallest ant species in the Midwest. The workers are about 1/16 of an inch long, and they are smooth and shiny with yellow to dark brown coloration. They possess a stinger at the base of the abdomen.
Habitat
Thief ants are able to nest in a variety of places. They may be found in exposed soil; under objects like stones and logs; and inside decaying wood and tree stumps. Thief ants have the habit of nesting in or near the nests of larger ant species. Often times, they feed their own colony members with food stolen from the host and devour host larvae and pupae.
Thief ants can nest indoors. Under floorboards and behind walls and baseboards are common places to find thief ant nests. If they invade houses, it is generally during hot weather. These ants can be quite persistent in their nesting activities.
Life Cycle and Seasonal History
A thief ant colony may contain several hundred to several thousand individuals. Winged males and females swarm in late summer and early fall to mate. After mating, the queens can establish new nests and colonies on their own. Workers develop from egg to adult in about 52 days.
Human Interaction and Urban Impact
Thief ants are not medically or economically important pests. Thief ants may bite when disturbed, but due to their small size, bites will likely go unnoticed. Any medical questions or concerns related to a thief ant bite should be directed towards a physician.
Finding thief ants indoors does not always mean the ants are nesting indoors. These ants are known to travel a long distance in search of food, and they often have well-defined trails. Although a nuisance, thief ants do not cause significant damage.
Prevention and Management Approaches
Thief ants feed on both plant and animal products, but they are especially attracted to food high in protein like grease, meats, and dairy products. Foods, particularly meats and oils, should be kept in tightly sealed containers. Sites of food preparation should be kept clean, and trash cans into which food is dumped should be taken out on a regular basis. Recyclable containers should be rinsed well before storage. Potential openings into the house or building, such as a windowsill or under a door, should be sealed to prevent ant entry.
Thief ants may be difficult to eradicate due to their small size and the locations of their nests are usually in inaccessible areas. In cases where an indoor nest is found, treating cracks near the nest with a liquid insecticide may suppress the population for some time. Placing insecticidal baits near the nest is a better long-term option. The effectiveness of the bait is dependent on the availability of other food sources in the building. Available ant baits may need to be mixed with a grease or oil, like peanut butter or vegetable oil, to make them attractive to thief ants. Always use precaution and follow the label carefully before using any insecticide. Insecticides have a certain amount of toxicity to mammals; children and pets are especially at risk.
Other Online Resources
For information regarding labels of chemical control options, please visit NPIC MAPL
