Odorous House Ant



The odorous house ant Tapinoma sessile is one of the most common indoor pests found in North America. This species is found from coast to coast although it enters homes and building more often on the west coast for some reason. These small black ants invade buildings looking for sugary or sweet food items. They locate their nests in small voids and crevices behind wall voids. These small ants enter the building by climbing up through minor cracks in the foundation, often entering gaps next to door frames and floor-wall junctions. Odorous house ants devour jams, jellies, honey and other sweet in kitchens and in eating rooms. These ants wander around the inside of the house and recruit large numbers of workers when they find sweets. Odorous house ants arouse concern when worker ants or winged swarmers are discovered inside and the first thing people usually ask is How do I get rid of them?


Odorous house ants produce a strong smelling offensive odor when threatened. It smells noxious and even a single ant can produce an odor easily detected by a person.

Collect a few specimens on scotch tape or in vials (learn how) and send them (dead) in an envelope to your local university or extension office for identification. Worker odorous house ants are small, less than 1/8 inch and often numerous inside a home. With a small hand lens you may be able to see a single petiole or node between the main body and the gaster. Odorous house ant queens and males may swarm inside. Foraging ants are usually active on the floor and on counters and shelves. During warmer days a number of winged ants may swarm inside and they are usually trapped near a window as they try to escape towards the sun. When you see winged ants, you can predict that the nest is probably several years old and may have more than 3,000 workers.


The odorous house ant in nature occurs primarily in disturbed areas, where it nests under stones and under logs in open fields. Colonies can become quite large, numbering in the tens of thousands. A single queen produces enough eggs each day to replace any workers killed in action or dying of old age (about one year). Odorous house ants do not have a sting, they squirt a noxious chemical for defense.


Odorous house ant workers recruit quickly to sweet food and are thus highly vulnerable to elimination by baits.

It is not that important to locate the odorous house ant nest since it is unlikely that these ants are damaging a structure in any way. Baits are very effective when fresh and properly placed, and are generally preferable to contact insecticides in most situations. Permanent solutions to large odorous house ant infestations require the placement of many bait stations with enough bait to last for several weeks. Look for baits containing toxicants that are slow acting and allow time for the bait to be spread throughout the colony and especially to the queen.

Click to see some ant baits

Take the time to check on the bait to see if the ants are feeding. A circle of ants feeding together at a single bait station is a good sign. Do not place out large quantities of bait in a single location or the ants may try to bury the bait without feeding on it. Within one to two weeks all signs of ant activity should cease.


If you prefer to use a pest control vendor, then the following guidelines should help you choose a reputable firm.

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