This tropical species of ant is small; the worker is just 2mm long and the larger queen is usually between 3 and 4mm long. They are pale yellow in colour with darker red and black markings on their abdomens. They can also be recognised by their distinctive ‘double waist’.
Their appearance is similar to that of thief ants which means that the two species are often confused. The easiest way to tell them apart is by looking at the antennae. The pharaoh ant has a three-segmented antennal club, whereas the thief ant’s is two-segmented.
Unusually for an ant species, the pharaoh ant has many nests, each with a separate queen within a single colony. Each new queen lives as long as 39 weeks and will lay around 300-350 eggs during her egg-laying spell. It takes around 45 days for a pharaoh ant to grow from an egg to an adult.
As a nest grows, worker ants will relocate a developing brood to form a new satellite nest. Due to their tendency to form multiple nests and the fast growth of their colonies, infestations can spread rapidly and be difficult to control.
The pharaoh ant is becoming increasingly common in large structures with central heating such as hospitals and high-rise blocks of flats, where they can be a threat to public health. They are also a significant nuisance in food preparation areas because of their attraction to sweet foods.