Wood ants are approximately one centimeter long, brown-black and social insects that belong to the order of hymenopteran. They form large, well organized colonies that build over one meter high anthills from needles and branch pieces. The wood ants in one colony are related to each other. There are five species of Formica rufa -ants in Finland.

Wood ants prefer coniferous forests as their habitats and built their anthills on bright places to the southern side of trees or stones. Wood ants move a lot around their hills which is why there are paths clear of vegetation on their routes. Wood ants occur in the boreal zone.

Wood ants have an impact on the function of forest ecosystems because they shape the ground, circulate nutrients as well as provide a habitat for many other invertebrates. Wood ants feed on other insects, carcasses, seeds and honeydew of greenflies. For example, bears and woodpeckers eat wood ants.

Wood ants belong to the key species of northern coniferous forests. As a consequence of silvicultural measures, they may temporarily abandon their anthills, but come back when the forest grows again.