Like sea crabs, they are crustaceans. Soil is one of the richest of all wildlife habitats, teeming with tiny creatures. Scientists estimate that there are 2.5 million spiders in the soil beneath every hectare of pasture land, as well as 25 million insects and 1500 million mites - and if you weighed all the worms in the soil beneath a field of sheep they would weigh more than the sheep. All these creatures play a vital part in maintaining the soil structure and in recycling nutrients. Worms air soil by burrowing through it, and improve its texture by eating and then excreting it.
Bacteria help to turn rotting plant and animal matter into soil nutrients essential for plants.
The leaf litter on the soil surface is as teeming with life as the soil itself. Bacteria, fungi, worms, snails and hundreds of different arthropods all live on the rotting plants and help turn them into the rich humus that makes the soil fertile. Earthworms wriggle through the soil by contracting some of the segments that make up their long, thin bodies. As they move, they take soil in through the front of their bodies and excrete it through the end. Garden snails tend to emerge to feed only when it is damp.