An OHA worker feeds on a bit of gel bait. Photo courtesy of, and copyrighted by, Gene White, pmimages@earthlink.net

Tapinoma sessile

Alias: Odorous house ant

Description

• The odorous house ant (OHA) gives off a pungent, unpleasant rotten coconut odor when crushed, which led to its common name.
• Monomorphic workers are 1/12- to 1/8-inch long, and are brownish-black.
• OHA has a 12-segmented antenna without a club.
• They are monomorphic, or all of similar size.
• Frequently confused with Argentine ants, OHA can be easily distinguished by its darker color and abdominal gaster that overhangs and hides its flattened pedicel.
• OHA can be confused with velvety tree ants (Liometopum occidentale) because of the similar odor produced, but can be distinguished by the velvety tree ant’s vertical node.

Life Cycle

• Colonies are large, with several thousand workers and many active queens.
• Winged reproductives appear May through July.

Behavior

• Nests are located indoors and outdoors, in a variety of situations.
• Outside, nests are shallow and can be found under a board or stone.
• OHA can be found in mulch, and under logs and rocks.
• In structures, nests frequently can be found behind exterior sheathing/siding and masonry, in the layered construction of exterior walls (especially under window sills), damp roofing, and under flooring and toilets.
• Workers forage along regular trails.
• OHA use edges to guide them as they move from place to place. Indoors, these can be siding, home foundations, baseboards, counters, wires or pipes. Outdoors, these can be trees or vines.
• They may forage in tubes abandoned by subterranean termites.

Food

• OHA prefer sweet foods, such as sugars. They also will feed on dead insects, pet food and grease.
• Outdoors, OHA feed on aphid honeydew and nectar from flowers and buds.
• They move indoors late in the year when honeydew, one of their primary foods, becomes less abundant.
• Honeydew availability also may be reduced at other times, such as during and after excessive rainfall. As a result, OHA may move indoors in search of food.

Range ➔ OHA are found throughout the United States and southern Canada; they are common along the West Coast, Atlantic coastal and New England regions, and in the mid-southern region of the United States.

Prevention ➔ Eliminate moisture and water sources; remove food sources by keeping food sealed; prune trees and ivy so they do not touch the structure; seal entry points into structures; store firewood and lumber away from the home; move garbage cans away from the structure.

SOURCES:

Truman’s Scientific Guide to Pest Management Operations

Penn State Extension

University of Tennessee Extension