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Wood Ants

The Superfamily Formicoidae contains just one very large family - the Formicidae (ants) - with probably something like 10 000 species in the world. In Britain, there are about 36 species. All ants are social insects, living in colonies and usually having female (queen), male and worker castes. The bulk of the ants in a colony are workers. These are all wingless females.

Wood ant illustration

The Wood Ant, Formica rufa, is the largest British ant. It is found on heaths in both deciduous and pine woodlands, where it builds nests of twigs, leaves and pine needles. These nests often reach two metres across and one metre in depth, and at the height of the season may contain up to 300 000 individuals. The ants occupy galleries in both the mound and the soil beneath, where the nest will extend downwards at least as far as the mound is high! They are most active on warm, dull, humid days, although they forage both day and night. The foragers are the worker ants, which are non-breeding females whose function is to collect food, to build, clean and repair the nest, and to defend the nest against predators and rival ants.

Cross section of wood ant nest

In the nest, the queen lays eggs throughout the summer, so that at any time there are larvae at all stages of development. Battles occur between ants from different colonies to establish territories. These territories range from about 270 to more than 1600 square metres in area, each one consisting of a network of permanent foraging trails formed around the nest and kept clear of obstructions, so that the nest material and food can be brought to the colony.

The ants feed mainly on aphids, flies, caterpillars and honeydew. Honeydew, which is 'farmed' from specially tended aphids, forms about 60% of their diet, another 30% comes from plant sap and resin from trees, 5% from fungi and the remainder from carrion and seeds. The worker ants bring the food to the nest and regurgitate it for the other ants. Much of the foraging takes place among the branches of tall trees and the Oak is by far their favourite - so much so that ants from one nest have been observed walking past a Sweet Chestnut and on for another 30 metres to forage on an Oak!

In addition to foraging over great distances from the nest, workers put considerable effort into keeping the nest at the correct temperature. If the mound is in danger of becoming too cool, they 'sunbathe' on top and then go down inside to release the heat stored in their bodies; if the mound is likely to get too warm, they open up vents on the surface to allow in cool air. When the nest is disturbed, the workers swarm out to confront the intruder, biting with their strong mouth parts and rearing up to spray formic acid from their rears. Through incredible aggression and sheer numbers, they are formidable opponents for most other inhabitants of the Wood.


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