Scottish wood ant (Formica aquilonia)
|Size||Worker length: 5 – 10 mm (2)|
Queen length: 12 mm (3)
The Scottish wood ant is classified as Nationally Scarce in Britain (4) and as Near Threatened (NT) on the IUCN Red List (5).
All wood ants are red and black in colour and are the largest ants in Britain. Examination of the head allows species to be identified (3). The Scottish wood ant, (Formica aquilonia) has a fringe of hairs on the rear of the head that does not extend down to the eyes (6). The thorax is reddish-brown and is paler than the head; it has fewer, shorter hairs than the other British wood ants (7).
The Scottish wood ant is found throughout the Scottish Highlands (3), reaching as far north as Ross and Sutherland. It reaches west and south to the West Highlands and Argyll. It has been found on the Islands of Skye and Arran and there is a single strong population in Armagh, Northern Ireland (4). Elsewhere, this ant occurs in Europe from the Alps to Siberia and from Arctic Norway in the north as far south as northern Italy (2).
The Scottish wood ant can thrive in undisturbed pine forest and old birch woodland and has also been recorded on the edges of plantations (3) (4).
Wood ants are social insects that live in very large colonies. Most of the individuals found in these colonies are non-reproductive females known as workers. These individuals carry out the foraging and brood-care duties for the colony. The queen is the only member of the colony to lay eggs (3). At the beginning of spring each year, unfertilised eggs are produced, and these develop into males. Other eggs that are produced at this time and are fed more become queens, while others develop as workers. During June, usually on a warm humid day, huge numbers of winged reproductive males and queens leave the nest en masse and engage in a mating flight known as the ‘nuptial flight’. After mating the male soon dies, the queen sheds her wings, and searches for a suitable location to establish a new nest (6). She will not mate again during her lifetime, but stores sufficient sperm inside her body to fertilise all her future eggs (3).
Scottish wood ants create very large dome-shaped nests that are ‘thatched’ with pine needles. These nests typically have one elongated side, to maximise the sunlight falling on the colony (3). Ants are known to have very close mutually beneficial associations with many other types of organism (8), and it has recently been discovered that the nests of the Scottish wood ant contain many earthworms (Dendrodrilus rubidus). It is thought that the earthworms benefit from this association as the nests provide a relatively warm, constant habitat, and the ants benefit in turn as the earthworms keep the nest free of damaging moulds and fungi (9).
Wood ants are carnivorous, and workers carry a wide variety of prey back to the nest along trails that extend throughout the territory. The workers also tend aphids for the sugary ‘honeydew’ that they exude from the anus; the aphids gain protection from predators in return for this service (6). Studies in Scotland have shown that each F. aquilonia worker brings an average of one and a half times its own weight in food back to the nest daily. Five to six trackways leave each nest and lead to the trees where most of the foraging takes place. Many workers may leave the trackways to forage in the surrounding area at random (7).
The main threats facing the Scottish wood ant in Britain include the widespread loss of undisturbed native pine woodland and unsuitable management of remaining woodland (4). Modern forestry techniques, including under planting with non-native tree species are detrimental to this and other species of wood ant, as they cause too much shade for the ants to prosper. Disturbance, the use of insecticides and overgrazing are also problems (3).
The International Union for the Conservation of Nature (IUCN) has identified the Scottish wood ant as Near Threatened. It is listed as a priority species under the UK Biodiversity Action Plan (UK BAP). The Species Action Plan for this ant aims to maintain all current populations and the present range of the species in the UK (4). Research into the habitat requirements and ecology of this species is underway; it is hoped that the results of these studies will guide successful conservation action in the future (3). Wood ants are known to be ‘key-stone’ species in the ecosystems of which they are a part, playing a vital role in maintaining the delicate balance between organisms in the ecosystem. When wood ants are lost from an area, this delicate balance is disrupted. For example many species that the ants prey upon in turn feed on the needles of Scots pine (Pinus sylvestris), so the loss of the wood ant may have disastrous results. Their conservation is therefore of the utmost importance, not only for the species itself, but for the entire Caledonian Forest they inhabit and all the species relying on that habitat (3).
For more on British wood ants:
The Caledonian Forest Information Centre Trees For Life species profile on wood ants:
For more information on the Scottish wood ant:
BBC Wildlife Finder:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
- Thorax: In insects, the three segments between the head and the abdomen, each of which has a pair of legs.
NBN Species Dictionary. (Feb 2003). Available on-line from:
US Department of Agriculture (November 2003):
Trees For Life - Caledonian Forest Information Centre. Woodants (November 2003):
UK BAP Species Action Plan for Formica aquilonia. (November 2003):
IUCN Red List (April, 2011):
- Skinner, G. (1998) British wood-ants. British Wildlife, 10 (1): 1-8.
- Brian, M.V. (1977) Ants (New Naturalist). Collins, London.
- Höldobler, B. and Wilson, EO. (1990) The Ants. Springer, New York.
- Laakso, J. & Setälä, H. (1997) Nest mounds of red wood ants (Formica aquilonia): hot spots for litter-dwelling earthworms. Oecologia111: 565-569.