Ants nests are relatively scarce in the ridge region and the construction of large-scale colonies is not helped by the barren nature of the ridge. However, as elsewhere, nests are constructed in the most favourable locations for warm, sunny conditions and almost without exception they are found by the trails.
The most commonly found nest builder among Finland’s ants species is the red wood ant, which belongs to the Formica rufa group, including a variety of species that have adapted to different living conditions. The nest is built from pine needles and twigs and, as their Finnish name indicates, it is a large anthill. In a large colony there can be half a million workers and over a hundred queens; each colony can contain several dozen nests and between each nest there may be routes that are hundreds of metres long. The paths usually lead to tree roots as the ants gather honeydew from the aphids that feast on the tree’s sap. Honeydew is the ant’s most important nutrition, thus there is a symbiosis between aphids and the ants; in exchange for regular honeydew the ants keep the aphids enemies at bay. In addition to the honeydew, ants will eat other insects, spiders, and even large earthworms. They can also eat carrion from small mammals. A large anthill may have been inhabited for up to fifty years, but usually the nest will be abandoned after ten years of use; around a large nest there are often small satellite nests that are only inhabited for a few years.
Anthills that have been destroyed are a common site as they are often a source of food for birds. In wintertime, a black woodpecker can dig a hole into the nest and penetrate through to where the ants winter in densely-packed heaps. A small anthill is usually destroyed as a result of such an attack, but a large nest always has a few survivors. There is also another predator ant’s fear, in the summer, badgers will invade in search of juicy larvae.
Photo: Jyrki Oja