Pharoah Ant

Common Name: Pharoah ant
Scientific Name: Monomorium pharaonis

Introduction. This ants common name resulted from the mistaken belief that it was one of the plagues of Egypt in the time of the Pharaohs. Pharaoh ants are thought to be native to the African region. Pharaoh ants are found throughout the United States and have been strongly implicated in the spread of various disease pathogens in hospital settings.

Recognition. The workers are 1/16 inch long and the body is yellowish to orange, with a dark tip at the rear of the gaster (enlarged part of the abdomen). Under magnification, the antenna is 12-segmented, with a 3-segmented club. The thorax profile is unevenly rounded. The waist (abdominal pedicel) is 2-segmented (two nodes) and a stinger is present but seldom used. Queens are about 1/8 inch long and slightly darker in color than workers. Queens are produced with wings but the wings are removed soon after mating, Males are about 1/16 inch long, winged, black in color, and possess straight antenna straight, not elbowed. The males are very gnat-like in appearance.

Similar Ants. Thief ants (Solenopsis molesta) are tiny and yellow-orange like pharaoh ants but have antennae that are 10-segmented with a 2-segmented club.

Biology. The colonies tend to be large with workers numbering in the thousands to several hundred thousand. There are usually several hundred reproductive females present in such a colony. Although winged reproductives are produced, there are no flights of swarmers. Rather, mating takes place within the nest. New nests can be formed by budding with as few as 5 workers, 10 pre-adults (larvae and pupae), and one queen migrating from the original colony. Developmental time (egg to adult) for workers is about 38 days at 80F Workers live about 9 to 10 weeks, with only up to 10% out foraging at any given time. Queens live 4 to 12 months, and males die about 3 to 5 weeks after mating.
These ants are of particular importance in hospitals where they will enter wounds, enter in-use IV bottles, seek moisture from the mouths of sleeping infants, etc. More than a dozen pathogenic bacteria have been found on pharaoh ants collected in hospitals.

Habits. Inside, Pharaoh ants nest in warm, humid areas near sources of food and or water. Nests are usually located in inaccessible areas such as wall voids, behind baseboards, in furniture, under floors, and between linens. Also pharaoh ants will nest in debris collected on flat roofs and those nesting inside will venture outside onto flat roofs in warm weather for water and food (dead insects). They typically enter and exit via poorly caulked and defective windows, under the flashing, and through weep holes in brick veneer.

The workers forage widely from the nest in search of food and water, and establish trails to food and water sources. They commonly use electrical and telephone wires as a highway system to travel through walls and between floors. Pharaoh ants are common problems in commercial food handling establishments such as hotels, grocery stores, hospitals, and in apartment complexes.

Outside, these ants seem to be of little importance as pests. In the temperate northern areas of the United States, they usually cannot survive outdoors year round. They have a wide preference in food, ranging from syrups to fruits, pies, meats and dead insects. They use carbohydrates primarily for maintenance; whereas protein is primarily required for larval development and egg production by the queens.

Cultural Control & Preparatory Measures. A thorough initial inspection is crucial to determine ant locations. Pre-baiting with non-toxic mint-apple jelly can help to locate ants. Outside, an inspection of the building perimeter, including thresholds and window ledges, for possible ant activity is helpful as well.
Quickly clean up food (including pet food) and beverage spills from floors, counters, porches and decks to discourage foraging by these ants indoors and near residences/buildings. Food items should be stored in airtight containers, if possible.
Do not attempt to control pharaoh ants using over the counter insecticide products because this may make the problem worse, as mentioned above. Nor should one disturb or contaminate the foraging ants or the bait stations that have been installed by the technician.

Professional Control. The typical use of repellent liquid or dust insecticides (versus non-repellent baits) actually makes the situation worse by causing the colony to fracture (bud) into several colonies. Immediately after such an application, a false sense of control is perceived during the 7 to 10 days it takes for the colonies to relocate and reorganize, because ants are not seen. Then the ants resume their foraging activity and again become visible. This cycle can be repeated many times.

Baiting is usually the only method of effective control. For this reason, Rottler technicians employ multiple strategic placements of bait stations known to be attractive and effective against pharaoh ants. Baits are located as close as possible to where the ants are entering/exiting from walls, ceiling, appliances, etc., but such that the likelihood of bait station disturbance is minimal. Technicians place baits as close to foraging lines of ants as possible without disturbing them.
If the Pharaoh ant infestation is in a multifamily building, the only way such an infestation can be eliminated is inspection and treatment of the entire building. Otherwise, ants will move from non-treated units into ant-free units.

If the ants are nesting in the ground on the outside, a perimeter barrier application utilizing a fine granular insecticide bait or residual insecticide formulation is made. Window sills have proven to be strategic baiting zones as well.