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Wood Ants

Wood Ant

The Wood Ant, also known as the horse ant, is a woodland-dwelling member of the Formica rufa group of ants. There is also a Scottish Wood Ant (Formica aquilonia) as well as a Hairy Wood Ant (Formica lugubris) which is also known as the Northern Wood Ant.

If you look at a Hairy Wood Ant through a microscope you’ll see it has hairy ‘eyebrows’.

Northern Hairy Wood Ants are polygamous which means there can be more than one queen in the nest. Queens can live for up to 15 years, whereas workers live for about a year.

Formica rufa is aggressively territorial, and will often attack and remove other ant species from the area.

They have large mouthparts and like many other higher ant species are able to dispense formic acid from the abdomen as a defence mechanism. Formic acid has been collected from Formica rufus. The ants were crushed up and distilled by John Ray, an English naturalist, as early as the 17th Century.

The Green Woodpecker and the Jay will fly into an ant nest to be sprayed with formic acid which cleans them of mites.

The Wood Ant is the largest native ant species of the British Isles. Workers can measure from 8-10mm in length.

Wood Ants have a symbiotic relationship with aphids. The ants effectively ‘farm’ them by gently stroking them to release honeydew which is used to feed the ant pupae. In return the ants protect the aphids.

Formica rufa is commonly used in forestry and is often introduced into an area as a form of pest management.

Worker ants find food by hunting and scavenging, they locate prey by vibration although they can see for up to 10cm. They will quite often hunt in tree canopies reached by crawling up the tree trunks and although many return the same way a noticeable number choose to return by falling. More choose the ‘ant rain’ option when birds are also foraging in the trees.

Find out more about Wood Ants...


BBC Natures Calendar 

A Year in the Life of Ants – Radio 4  

BBC Wales Nature 

Natural History Museum Nature Navigator

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Watch and Listen

Iolo Williams take a closer look at just how impressive a Wood Ant nest is:

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Tips for viewing this species:

  • Check out woodlands and parks in good locations… have a look at your local Wildlife Trust website to see if there’s anywhere near you with an established Wood Ant population. Ants can be found in scattered woodlands throughout Britain. Coed y Brenin, near Dolgellay in Gwynedd and Glen Affric National Nature Reserve in Inverness are good places to see Wood Ants.
  • Wood Ants are most active from early spring to late summer.
  • Watch the worker ants as they march along pathways to-and-from the nest bringing food or building materials.
  • Watch the nest – don’t disturb it.
  • Take binoculars with you to get a closer look at the ants.
  • Find out how defensive the wood ants are by placing a piece of litmus paper on the nest.  Then watch as the ants attack it. Litmus paper measures acidity and alkalinity, acid turns it red. The paper should turn almost bright red as the ants cover it with their main weapon - formic acid.


The Wood Ant is commonly found throughout southern England in both coniferous and broad leaf broken woodland and parkland.  It builds large dome shaped nests covered with pine needles, twigs and leaves.

Wood Ant

The pine needles are placed in such a way that when it rains the water is shed and doesn’t flood the nest. The side of the nest facing the sun is slightly flattened and workers block and unblock the entrances and exits to regulate humidity. In the spring workers will swarm on the top of the nest absorbing the solar energy and taking the warmth back inside. The nest temperature is kept at around 25 – 30 degrees.

The nest acts as protection from predators and the elements and provides a stable environment for eggs and pupae.

Inside the nest is a network of several kilometres of tunnels. A mature nest can be home to more than a million ants. On hot days the workers will bring the eggs to the warmest part of the nest to speed up their metamorphosis.

Wood Ant nests can be more than a metre high and twice as wide. They have been known to extend more than two metres below ground. They are usually situated in woodland clearings, where they are exposed to the sun.

There are other invertebrates which live alongside ants. The beetle, lomechusa strumosa, is fed and protected by the ants and the worm, dendrodrilus rubidus, helps keep the nest from being overgrown with moulds and fungi.

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