Tapinoma sessile

School of Ants collection
Literature record

Tapinoma sessile

From Dr. Eleanor's Book of Common Ants

A.K.A.: Odorous house ant

Size: Workers: 2.4-3.25 mm

Where it lives: Odorous house ants nest indoors (under sinks and doormats and in insulation and dishwashers) and outdoors (under rocks and in garbage cans, potted plants and exposed soil).

What it eats: Honeydew, a sugary liquid made by small insects called aphids and scales, and other sugary food left out by humans. Odorous house ants also eat dead insects and spiders.

What’s the big deal?

One of the United States’ most common household ant pests, odorous house ants have a hard-to-tame sweet tooth that often leads them wandering across your kitchen counters day and night, looking for sugary snacks. At first glance, odorous house ants may seem like any ordinary ant—small and brownish black or black in color. But if you squish one odorous house ant and take a whiff, you’ll get an I.D. giveaway: They smell like blue cheese or coconut.

This odor is their primary defense against contenders. Unlike some other ant species, odorous house ants don’t have stingers to ward off trouble. When odorous house ants are disturbed, they run around erratically, spraying their odor from tiny sacs called anal glands in their rear ends. While this isn’t intimidating for human observers, their behavior is an effective deterrent against many adversaries their own size.

Odorous house ant colonies can range from fewer than 100 workers and one queen to more than 10,000 workers and hundreds of queens. They are virtuosos in the nesting department. Outside, odorous house ant nests have been reported under rocks, inside acorns, mulch, and leaf litter, in potted plant soil, in garbage cans, lawn furniture and cars. Indoors, they get a little more creative. Nests have been found under doormats, in dishwashers, and even under a toilet seat! Typically, odorous house ants prefer to nest near heat or water sources and in insulation.

Its great love of sweet stuff is one of the odorous house ant’s most remarkable traits. Laboratory studies show that, when given a choice, they make a bee-line for sugar over all other foods. Outdoors, they get their sugar from flower nectar and honeydew, a sweet substance produced by small insects called aphids. In exchange for a taste of honeydew, odorous house ants will even protect a species of butterfly caterpillars from potential predators.

Unfortunately, their love of nectarous treats sometimes leads to sneaking into people’s homes to filch food. Even though they can be a headache as they trundle across your Wheaties, odorous house ants are not to be feared. They don’t transmit diseases, they won’t cause structural damage to your house, and they can’t sting you. So take a minute, watch them forage and enjoy the beauty of nature inside your home.

If you don’t like odorous house ants pilfering your pancake syrup, keep your kitchen crumb-free and remove sources of standing water. Try to keep potential nesting sites like rich mulch and potted plants away from your house.

Find out more about this species at Antweb and see more photos at Alex Wild's photography site.