The pharaoh ant is a successful species that is considered to be a serious pest in many parts of the world.

Its Latin name is Monomorium pharaonis (Linnaeus).

Carolus Linnaeus (1707-1778), the Swedish botanist and taxonomist, thought that this species of ant had originated in Egypt. He mistakenly believed that this small, yellow ant was one of the plagues of Egypt in the time of the pharaohs and, having come to this conclusion on very little evidence, he named them Pharaoh Ants. In fact they are thought to have evolved from wasps in North or Tropical Africa and no link with Ancient Egypt and its pyramids has ever been proven.

They have since established a worldwide distribution, having been spread as an unintentional result of the commercial activity of humans and are now a particularly common pest in the USA and Japan. They cannot survive extreme cold but they have adapted to living indoors alongside human beings.

Looks and Lifestyle

Here is a description of pharaoh ants for entomologists amongst us:

Total length of workers around 2 - 2.5 mm. The body is unicoloured: yellow to reddish brown. The apex of gaster is dark. The sides of head are convex in front view with a smooth curve to a slightly convex occipital margin. There are two eyes each with around twenty facets. The mandibles each have four teeth. The paired longitudinal carinae on the clypeus are distinct, as is the metanotal groove. The posterodorsal margin of propodeum is more or less angulate. There are no standing hairs on the propodeal dorsum but there are erect hairs that are long and abundant on the head and gaster. The ventral outline of petiole is not strongly convex. Body surfaces from the head to the postpetiole are finely, densely, and distinctively, punctate. Body surfaces are opaque.

And for the rest of us: They are very small (2 millimetres long) and yellow but queens are longer (4mm), darker and sometimes have wings. Like all insects they have three segments to their bodies -- head, thorax and abdomen -- and they have six legs. Their antennae have eleven or twelve segments ending in clubs with three segments and this distinguishes them from thief ants whom they closely resemble but who have ten segments to their antennae and two segments to each club. The antennae of the males are not elbowed.

Pharaoh Ants are commonly found in kitchens and storerooms. They like places that are warm and humid. They will nest in any crack or crevice in a structure such as between bricks as well as in folded bags or newspapers. Pharaoh ants will also nest in and around appliances such as refrigerators or stoves that have food or water around them. In subtropical areas they will nest outside in leaf litter, piles of bricks, potted plants, under roof shingles and in debris on flat roofs.

Colonies of Pharaoh ants can become very large; they often contain as many as 300,000 workers with several hundred queens. There is no swarming and new colonies are formed by budding. Budding is when some of the workers, brood, and a few queens move to a new location. In warm climates where the ants can survive outdoors they will move from building to building. New nests can be formed with as few as five workers, ten pre-adults, and one queen.

Pharaoh ants are omnivorous. They feed on a wide variety of foods including fats, proteins and carbohydrates, particularly sugars, and will also take and kill small insects. They use carbohydrates primarily for maintenance; protein is required for larval development and egg production by the queens. They need moisture and in modern houses with very dry interiors they may sometimes be seen drinking from the water taps. The workers go some distance from the nest and establish trails to food and water sources. They sometimes use electrical and telephone wires as routes to travel through walls and between floors. Once a worker ant locates a food source during a foraging expedition it lays a chemical trail from the food to the nest. When workers return to the nest they excite other workers to follow the trail to the food source. The chemical trails are often many metres long.

Love and War

Mating takes place inside the nest. The development of eggs into adult takes about 38 days provided that the temperature is warm. Workers live about nine or ten weeks, with only ten percent going out to feed at one time. Queens live much longer (from four to twelve months) and males die about three to five weeks after mating. Nests spread by budding when food supplies are threatened. Thus interference with workers fetching food may well increase the number of ant colonies in an area.

Pharaoh ants are not warrior ants. Their stinger is present but not significant and is used primarily to capture small prey insects rather than for defence. They do not cause noticeable stings to humans: they do bite but not hard. Their principle form of defence against attack is the ability of the colony to bud as described above and it is this ability that makes them such formidable household pests.

Nasty habits

Control of pharaoh ants is necessary because they are believed to spread diseases. They are a common problem in hotels, grocery stores, hospitals, and apartments. More than a dozen pathogenic bacteria have been found on pharaoh ants collected in hospitals. Many of these bacteria are of medically important, opportunistic kinds including Streptococcus pyogenes, Pseudomonas aeruginosa and Staphylococcus epidermidis. Pharaoh ants will infest wounds, enter IV bottles while they are in use and seek moisture from the mouths of sleeping infants.