Identification

Earthworms have elongate tubular bodies consisting of many segments or rings. Most species are reddish brown but some have a banded appearance while others are a dirty whitish or greenish yellow colour. Mature earthworms have a distinctive saddle or clitellum about one third of the way down the body from the head end. Earthworms have no legs but they have small spines or spicules that help them grip the soil as they tunnel through it.

Although the cross section of an earthworm’s body is circular, when a worm’s body is fully extended, it can be relatively flat. This can cause confusion with some of the alien terrestrial flatworms that have become established in Britain, such as the Australian and New Zealand flatworms. Terrestrial flatworms have very flat, ribbon-like bodies and no sign of any segmentation or a clitellum.

Another worm-like creature, mainly found in heavier soils such as clay, is a terrestrial leech. These are greyish-green in colour with relatively flat bodies. Their bodies are finely segmented, with no clittellum, but they have a circular sucker on the underside of the rear end of their bodies.

Size

Mature earthworms are 2.5-12cm long but they have elastic bodies and may be longer when fully extended.

Distribution

Earthworms are found in most soils but may be scarce in soil that is very acidic or frequently waterlogged.

Status

There are 26 species of earthworm in Britain, of which 14 are relatively common. In some parts of Britain, earthworm populations are being depleted because of heavy predation by alien flatworms that have become established here.

Habitat preference

In damp soil with a high organic matter content, especially in compost heaps, grassland and deciduous woods.

Where to find in them in the garden

In compost heaps and in the soil in flower beds and under the lawn.

Role in the garden

Earthworms tunnel through the soil, creating passageways through which rainfall can drain and air can reach plant roots. Earthworms feed on dead plant material, such as fallen leaves, and help to recycle plant nutrients. Many animals eat earthworms and they form an important part of the diet of many birds and some mammals, especially moles, foxes and badgers. Some earthworm species produce wormcasts, which are their muddy excrement, on the surface. This can be a problem on fine lawns, particularly during autumn to spring when wormcasts are too wet to be broken up and dispersed by brushing or raking the lawn surface.