Description of odorous house ants
Odorous house ants are small ants about 1/8th inch long and dark brown in color. They are found throughout the U.S. and in spite of their name, are found both outdoors and as a pest in the house. Their name comes from the disagreeable odor similar to the smell of rotten coconuts, that is given off when the worker ants are crushed. Odorous house ants are identified by the apparent absence of an upright node at the petiole between the thorax and abdomen. There is a single node to the petiole but it is concealed by the overhanging abdomen.
Life cycle of odorous house ants
Odorous house ants commonly nest outdoors in the soil under stones, logs, mulch, debris and other items. They will also nest indoors in wall and floor voids, particularly in moist or warm areas. If only a few workers (wingless ants) are observed in the house it is an indication that they are nesting outdoors and entering the house in search of food. If winged swarmers are found indoors, or if workers are consistently seen in great abundance, it likely indicates they are nesting within the house.
Odorous house ants regularly forage for food along well-traveled trails. They feed on dead insects, sweets and meats. One of their favorite foods is the sweet honeydew produced by plant sap feeding insects such as aphids and mealybugs.
Management of odorous house ants
Control of odorous house ants should begin with an attempt to locate the origin of the ants. Careful and frequent observation may be necessary to develop an opinion about the source. Ants entering from outdoors can be discouraged by sealing as many cracks and gaps in exterior walls as possible. A insecticide labeled for use outdoors in ant control can be used to control individual ant hills near the house or to create a protective barrier to stop foragers from wandering into the house. For more information about insecticides please see this article.
Odorous house ant colonies inside the house can be treated with ready-to-use household insecticide sprays or dusts labeled for use against ants . Inject a small amount of spray or puff or sweep a small amount of dust into the nest area. In areas where workers are observed the ready-to-use ant baits can be placed on or along trails, being careful to exclude contact with the bait by children and pets. For more information about insecticides please see this article.
If no source of the ants is determined the sprays, granules and baits can be used according to label directions and indoors or outdoors as already specified in a broad-based attempt to control the pests. A pest control operator can be hired to complete the treatments described. Monthly treatment for a year or more should not be necessary for control.
Do you live in Iowa and have an insect you would like identified?
The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them. Please see our website for current forms, fees, and instructions on preserving and mailing insects.
Contact information for each states diagnostic laboratory for U.S. residents. If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.