[Pest Profile] Odorous House Ant

Description

The thorax of odorous house ant workers has no spines, and the petiole has one segment which, when viewed from above, is hidden by the rest of the abdomen (see illustration at right). There is a slit at the tip of the abdomen instead of a circlet of hairs. When alarmed, the workers scurry around with their abdomens raised in the air.

Biology

These ants swarm to mate from early May through mid-July, and also mate in the nest, forming new colonies by "budding" off the original colony. There are several generations per year. Workers and queens live for several years.

Habits

Odorous house ants often nest outdoors under stones, logs, and in the nests of larger ants. They also can nest indoors in wall or floor voids, around heat sources, (e.g., hot water pipes and heaters, crevices around sinks and cabinets). Odorous house ants travel in trails and prefer sweets, although they eat almost any household food. They usually invade structures during rainy periods after honeydew on plants has washed off.

Control

Odorous house ants are difficult to control. They prefer sweets but are not easily controlled using sweetened baits. Baits should be placed where ant trails have been established or in locations where the ants have been sighted. Unless using containerized baits indoors, baits should be placed so they are inaccessible to children and pets. Sweet baits are the most effective, but if acceptance is low, a protein bait should be considered. The most effective control is accomplished by following ant trails, locating the nest, and treating them with a residual insecticide. Exterior nests should be drenched with a liquid formulation. Nests in wall voids are more easily treated by aerosol injection or application of a dust formulation. When the nests cannot be located, a barrier spray should be applied to foundations and the soil immediately adjacent to the building. This is effective in repelling foraging workers and preventing them from re-entering the structure.