Odorous House Ants (Tapinoma sessile)

The Odorous House Ant is an invasive species found throughout North America. It can survive the mild Seattle winters outside and is a common and versatile structure-infesting pest. This pest is often found foraging in large numbers for food inside a structure and has become one of the more difficult ants to completely eradicate because of its behavior and biology.

Identification

Odorous House Ants are tiny ants, about 3 mm in length (or about an eighth of an inch) and are dark brown to black in color. They can be taxonomically identified by having a single node that is hidden from above by the abdomen. Outside of ghost ants, they are the only species with the hidden petiole node.

Life Cycle and Behavior

Like all ants, Odorous House Ants live in social colonies. These colonies are made up of different cast members, workers and reproductives. Swarmers first appear in the early summer months. In the spring, workers begin to forage and queens resume their egg laying. Colonies can be exceptionally large, ranging in size from several hundred to over 100,000 individuals. In addition, Odorous House Ant colonies can produce hundreds of queens and thousands of workers. Whenever the colony feels threatened, the ants will break off and form multiple satellite colonies through budding. Budding occurs when the colony becomes alarmed and the queens and workers break away from the primary colony and relocate to different areas in and around a structure. After a few months, the different colonies increase in size and can quickly overwhelm a homeowner or tenant.

Odorous House Ants are very opportunistic and can nest in just about any location both indoors and out. On the outside, Odorous House Ant nests are usually shallow and can be found in mulch, soil, debris, logs, stumps, and even under stones or outdoor furniture. Indoors, the nests are usually found in wall voids, around hot-water pipes and insulation, behind paneling, under carpets or beneath the floor. The nests tend to be mobile and colonies relocate fast and often in response to changes in weather and any disturbance. 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 food. 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 Methods

Treatment for Odorous House Ants depends on whether they are wandering into a building from outside or if they have already developed a colony inside the building. In addition, multiple satellite colonies may have already become established by the time the client calls a professional.

Odorous House Ants are easily alarmed and disturbing a nest or even crushing an individual may cause the colony to bud or relocate. Like Pharaoh Ants, a budding colony can survive with only a few queens and workers (less than 20). Treatments using a traditional repellent pesticide can actually drive the ants inside a structure, or cause an existing colony to bud into multiple colonies. Odorous House Ants do not attack each other (they will attack other ant species), and because of this there can be multiple satellite colonies within a small area all working together.

For this reason, it is critical that a professional pest control technician be involved to inspect and make the proper pesticide applications. Using the wrong product or applying it incorrectly can easily cause the ants to bud and eventually exacerbate the situation down the road. A professional technician from United Pest Solutions will inspect the situation, verify the type of ants present, and consider multiple approaches involving non-repellent residual sprays or baits for this type of ant. There are only a couple of products that effectively work with Odorous House Ants and these are sold only to trained pest management professionals who can apply them in specific manner for there to be an effective long term solution to the ant activity.

What Can You Do to Help?

• Do NOT spray! With this type of ant when you spray you will scatter them into other areas of the building. Because this scatters them it will make elimination of the colonies even more difficult.
   
• Trim bushes and trees. Preventing access through plants or trees to your building or home will ensure applications from your pest management professional are much more effective.
   
• Do not disturb them. If you suspect you know where a colony might be hiding, allow a trained technician to treat the area. Disturbing the colony will only cause them to scatter and form multiple colonies.
   
• Consider a Long Term Program. There is no quick method to eradicate this pest. Even when colonies are eliminated inside, there may be colonies on the outside of the building that may easily move in if there is not a proactive program in place to prevent it.