Over three thousand different earthworm species have so far been discovered, of which only about twenty-six species are present in the UK.

It is a common misconception that if you cut an earthworm in half it makes two new earthworms. Although they can regenerate to a small degree, usually both halves die.

Earthworms are divided into up to 100 segments, each with four pairs of small bristles used for movement. Larger segments form a saddle located behind the head-end.

Earthworms have five pairs of hearts, positioned inside the head.

The lob worm is Britain's largest earthworm - up to 35 cm in length when moving. It lives in deep vertical burrows in the soil and can anchor itself by broadening its tail to grip the sides of the burrow. Lob worms emerge at night to feed on fallen leaves and other decaying plant material. They can reach populations of 20-40 per square metre in an average sized garden lawn.

The green worm is widely distributed in the UK and is often the most numerous earthworm in all but the most acid of soils. It is a small to medium-sized earthworm up to 8cm in length when moving.

Earthworms usually live in the soil's top few centimetres, but will burrow deeper to find essential moisture if the earth dries out or freezes. Earthworms are vital in maintaining soil structure and fertility, as they aerate the soil, improve drainage and bring nutrients to the surface.

In Ancient Egypt, earthworms were considered so indispensable to the agricultural economy that Cleopatra declared the earthworm sacred, and any export of earthworms was subject to the death penalty.

Although earthworms have both male and female reproductive organs (hermaphrodite), they still need to find a mate and exchange sperm before they can reproduce. They make a cocoon in which they deposit both eggs and their partner's sperm - live worms emerge later.

Earthworms are an important source of food for plenty of creatures, including hedgehogs, foxes, moles, many birds, slow worms and amphibians.

Charles Darwin studied earthworms extensively over many years in the garden where he lived at Down House, Kent, and the surrounding area. His pioneering work showed the important role played by earthworms in maintaining the health of the soil. He even kept earthworms in flower pots in his drawing room, and persuaded his wife and children to try the effect on them of music and loud noises.