SCIENTIFIC NAME: Tapinoma sessile Subfamily: Dolichodorinae

SIZE: 1/10 to 1/8 inch (2-3mm)

COLOR: Dark brown to black

DESCRIPTION: Odorous house ants are tiny, about 3 mm in length, and are dark brown to black in color. They can be taxonomically identified by having a single node on the petiole that is hidden from above by the abdomen. However, odorous house ants are most easily identified by the coconut odor that is produced when their bodies are crushed. It is from this odor that they get their name, odorous house ants.

HABITAT: The odorous house ant is found throughout North America and is a common house-infesting pest in New Jersey. This pest is often found foraging for food in long trails over household surfaces and can contaminate food products. Although these ants do not bite or sting, they are a persistent nuisance pest once they begin foraging indoors in large numbers.

These ants are almost always seen foraging in large numbers. When alarmed, the workers will run about in an erratic fashion with their abdomens raised in the air.

Life Cycle: Like all ants, odorous house ants live in social colonies. These colonies are made up of different cast members (workers and reproductives). Male and female reproductives are often called winged swarmers.* Swarmers first appear in the early summer months. Male swarmers will emerge from the parent colony first, followed by the new queens. A few days after mating, males usually die and the mated females begin new colonies. When a new colony is initiated, a queen lays a small batch of eggs and tends the larvae that hatch. The adults that develop become workers and take over colony labor activities. Once a colony has been established, queens will continue egg laying until late fall. During the winter months adults are inactive and the larvae slow their development. In the spring, workers begin to forage and queens resume their egg laying. Larval development and production increases so the colony can grow substantially during spring and summer. Colonies can be very large, ranging in size from several hundred to over 100,000 individuals. In addition, odorous house ant colonies can produce hundreds of laying queens and thousands of workers.

*Ant swarmers are sometimes misidentified as termite swarmers. Ants can be identified by having the front wings larger than the hind wings. Wings on termites, however, are considerably longer than the body and both wings are the same size.

Behavior: Odorous house ants are very opportunistic and can nest in many different places both indoors and out. Outdoors, odorous house ant nests are usually shallow and may be found just underneath the soil surface. These nests may be found in mulch, soil, debris, logs, stumps, under stones and under plastic outdoor tarps. Indoors, nests are usually found in wall voids, around hot-water pipes and heaters, behind paneling, under carpets or beneath the floor. Sometimes these colonies can become so large that they eventually bud. Budding is a process by which the parent colony splits to form satellite colonies. The satellite colonies remain inner-connected to the parent colony by foraging trails. These trails provide for the exchange of workers, food, and larvae.

Odorous house ants forage both night and day and eat many types of foods. They eat live and dead insects but are also very attracted to sweet foods. They especially like the honeydew that is produced by aphids and mealybugs. Many colonies of odorous house ants tend or herd aphids and mealybugs to collect the honeydew they excrete.

Control:

Non-Chemical Control: The best way to control odorous house ants is prevention. Good sanitation is a vital part of an effective ant prevention program. You should remove potential food sources inside the home by wiping up spills and counter tops and by storing foods in sealed containers. These measures will help remove potential food sources that are attractive to odorous house ants. If ants are seen coming into the building from the outside, then they can be discouraged by sealing up holes, cracks and crevices in the structure. Odorous house ants can also be discouraged from entering the home by removing potential harborages that may serve as nesting sites such as: debris, stacks of firewood or lumber. Trimming back vegetation and landscaping so that they do not contact the building will also eliminate possible routes of entry into the structure from the outside.

Even with preventative measures, control of odorous house ants is difficult. Control can be accomplished if the ant nest(s) is located. Sometimes the nest can be found by making careful observations and following the foraging trails back to the nest site. Once the nest is found it should then be removed. However, nest location is difficult and often impossible. Therefore, there are several alternative approaches using insecticides that can be taken to control an infestation.

Chemical Control: If the nest cannot be located, then baiting is the preferred method for controlling an odorous house ant infestation. An ant bait is a sugar or protein based food source that is combined with a toxicant. By placing the bait along an ant trail, foragers will be able to find the bait and return it to the colony without you having to locate the nest. The most effective ant baits have a slow acting toxicant that allows the ants to pick up the bait and survive long enough to bring it back to the nest and share it with other members of the colony. In this way, the entire colony can be controlled. It is important when using baits that you do not use a chemical spray to kill trailing ants. Spraying the ants will prevent them from returning to the nest and sharing the bait with the other ants. Chemical sprays may also contaminate baits making them repellent so that the ants will no longer feed on them. Spraying the ants can also disrupt the colony causing them to relocate or split into several different nests. Consult the Virginia 2001 Pest Management Guide, Home Grounds and Animals (VCE Publication 456-018) for control recommendations.

If the nest(s) can be located but cannot be removed (locations where access is limited), then insecticidal dusts can sometimes be used to control the infestation. If colonies are found nesting in a wall void(s), they can be treated by drilling a 1/8 to 1/4inch hole in the immediate area and injecting an insecticidal dust directly into the void. The hole should immediately be sealed after treatment. Always read and follow the labels before applying any pesticide.