Odorous House Ants

Scientific Name:Tapinoma sessile (Say)
CLASS/ORDER/FAMILY: Insecta/Hymenoptera/Formicidae
METAMORPHOSIS: Complete

Introduction:

The pungent, "rotten-coconutlike" odor given off when this ant is crushed gives it its name. It is a native species and is found throughout the United States.

Recognition

Workers monomorphic, about 1/16-1/8" (2.4-3.25 mm) long. Body brown to black. Antenna 12-segmented, without a club. Thorax lacks spines, profile unevenly rounded. Pedicel 1-segmented, with small node/segment hidden/concealed from view from above by base of gaster. Gaster with anal opening slitlike, lacking circlet of hairs. Stinger absent. Workers emit a disagreeable, rotten, coconut-like odor.

Similar Groups

(1) Ghost ant (Tapinoma melanocephalum) with head and thorax dark but abdomen and legs pale.

(2) Argentine (Iridomyrmex humilis), crazy (Paratrechina longicornis), pyramid (Conomyrma insana), and dark field (Formica spp.) ants have node visible, not hidden by gaster; in addition, pyramid ants with thorax with single tooth on upper surface, field and crazy ants with circular anal opening surrounded by circlet of hairs and crazy ants additionally with antenna! scape (1st segment) at least twice head length and very long legs in relation to body size.

(3) Other small dark ants have 2-segmented pedicel and/or lack rotten coconut odor when crushed.

Biology

Odorous house ants have adapted to a wide range of habitats and thrive nearly everywhere from sea level to about 10,500 feet. They nest in sand, pastures, grass fields, forests, bogs, and houses, frequently under stones and logs. They also build nests under stumps and the bark of dead trees, in bird and mammal nests, plant galls, and debris.

Colonies may be composed of several hundred to 100,000 ants. There are usually many queens in a colony. Developmental time (egg to adult) is 34-83 days, varying with temperature during summer months, and up to 6-7 months during the winter. Colonies typically produce 4-5 generations a year. Although they probably mate both inside and outside the nest, the first swarmers appear from May to mid-July. The workers and queens live for several years. Individuals from different colonies are not hostile to one another and workers normally move along trails.

Odorous house ants are opportunists, nesting both indoors and outdoors. Indoors, odorous ants can nest in wall crevices, near heaters, water pipes, under carpets, beneath floors or sometimes behind paneling. Outdoors, odorous house ants place their shallow nests beneath soil as well as in logs, mulch, debris and under rocks.Like all ants, odorous house ants live in colonies. Each colony may contain two or more queens and over 100,000 workers. The queens of an odorous ant colony can produce thousands of workers and hundreds of reproductives.

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.

Odorous house ants forage for food night and day. Outdoors they prefer honeydew from aphids and mealybugs. When the honeydew supply is reduced in autumn, they may move indoors for food. Indoors, they eat meats, sugary foods, dairy products, pastries, cooked or raw vegetables and fruit juices.When alarmed by a predator, worker odorous ants will move in quick, erratic motions, raising their abdomens into the air.

Diet

Odorous house ants can feed on anything...insects, honeydew, seeds, plant secretions, but they do prefer sweets. Odorous house ants are extremely fond of honeydew and attend such honeydew-excreting insects as plntlice(aphids), scale insects, mealybugs, etc.

Habits

Inside, these ants usually construct their nests in wall voids especially around hot water pipes and heaters, in crevices around sinks, cupboards, etc. These ants prefer sweets but also eat foods with high protein content and grease such as meats and cheese.

Outside, they are often found in the nest of larger ants, in exposed soil, but mostly under objects. Workers feed on insects, seek honeydew and plant secretions, and even feed on seeds. They are extremely fond of honeydew and attend such honeydew-excreting insects as plantlice (aphids), scale insects, mealybugs, etc. They are most likely to enter buildings when their honeydew supply is reduced such as during rainy weather or with leaf fall in the autumn. When workers are alarmed, they run around in an erratic manner with their gasters/abdomens raised up.

Management

Control of foraging odorous house ant workers can be accomplished through the use of baits. The workers carry the baited material back to the nest, eliminating the colony. Many different types of bait are available to the homeowner in this regard. However, baits containing hydramethylnon, fipronil or boric acid are slower acting and do not kill the workers before they have had a chance to share the baits with the queen and developing immature ants. Choose baits designated for sweet-loving ants. Place the baits in areas where ant activity has been observed and make certain that children or pets cannot reach them. Maintain sufficient amount of baits to satisfy the colony by replacing used baits. It may require two weeks or longer to obtain control.

Control

Location of the nest(s) is crucial and can often be accomplished by following the trail of foraging workers back from the food source. Use of boric acid dust in the voids of outside ground-floor walls and infested interior walls along with barrier treatment is effective. Baiting is often required.