The Odorous House Ant

Common Name:
Odorous House Ants
Scientific Name:
Tapinoma sessile (Say)


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.


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 nodelsegment hiddenlconceated 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.


  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 antennae scape (lst 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.


Colonies may be composed of several hundred to 10,000 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.


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.