Odorous House Ants

COMMON NAME: Odorous house ant
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.

BIOLOGY. 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.

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.

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.