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Southern wood ant (Formica rufa)

Acid-spraying insects with a soft side. Southern wood ants roam our woods in huge gangs and have a surprising approach to finding their favourite food.

Southern wood ants spray formic acid to defend themselves.

Credit: Kim Taylor / naturepl.com

The southern wood ant is the largest UK ant, and winged queens like this one are even bigger.

Credit: FLPA / Alamy Stock Photo

Southern wood ants are very territorial.

Credit: Andy Sands / naturepl.com

Quick facts

Common names: southern wood ant, red wood ant, horse ant

Scientific name: Formica rufa

Family: Formicidae

Habitat: woodland

Diet: insects and invertebrates, aphid honeydew

Predators: birds, badgers may take eggs and larvae

Origin: native

What do southern wood ants look like?

The southern wood ant is the UK’s largest ant species. It is a reddish-brown colour, with a black head and abdomen.

Credit: Zoonar GMBH / Alamy Stock Photo

What do southern wood ants eat?

Southern wood ants are carnivorous and will actively hunt other insects and invertebrates such as caterpillars and spiders. However, their main source of food is honeydew, a sugary substance that is secreted by aphids (small insects that feed on plant sap).

To access this food source, wood ants have developed an unusual relationship with aphids. Ants will ‘tend’ to the smaller insects, stroking their abdomen with their antennae. This stimulates the secretion of honeydew. The aphids benefit from this relationship as the presence of the ants deters attacks from other predators.

Wood ants will climb trees to reach aphids. Juniper, Scots pine, sycamore, birch and oak are all important host species for the small insects. 

Quick facts

Research has found that a single colony of wood ants may consume a quarter of a tonne of honeydew annually.

How do southern wood ants breed?

Southern wood ants live in large, complex social groups made up of three groups: queens, workers and males. Each group fulfils a specific role to ensure the survival of the colony. Males mate with queens, who then produce eggs. Workers, which are all female, are responsible for feeding the colony and maintaining the nest in which it lives.

In summer, huge numbers of winged males and queens will emerge from the nest, mating in mid-air. With their role fulfilled, the males will die not long after mating. The queens will disperse before shedding their wings and looking to establish new nests elsewhere.

Colonies work together in complex structures to survive.

Credit: Paul Hobson / naturepl.com

Did you know?

When threatened by predators, wood ants can spray formic acid in a bid to defend themselves.

Where do southern wood ants live?

Southern wood ants are most numerous in the south of England and Wales, but can be found further north in smaller numbers. The species prefers to build its nests in open woodland glades that are well exposed to sunlight.

They are also fiercely territorial and will attack any ants from a different colony that enter their territory.

Credit: Alex Hyde / naturepl.com

Signs and spotting tips

Wood ant nests are large and conspicuous, meaning the species is easy to find. Look out for dome-shaped mounds of grass, twigs, or conifer needles.

Threats and conservation

The southern wood ant is relatively numerous in southern England and Wales, but has disappeared from much of the Midlands, East and North. Potential threats include loss and damage of woodland, overgrazing from deer and livestock and human disturbance.