Scabies mites can make people itch, and house-dust mites can bring on asthma attacks in some people. But mites are also helpful, playing a vital role in recycling nutrients in the soil. Even house-dust mites clean up dead skin. These are long, wriggling creatures with many legs. Centipedes are hunters with powerful jaws to devour insects, worms and grubs.
Most millipedes are herbivores, living on dead plants.
Snails and slugs Snails and slugs have soft, squidgy bodies. Snails are protected by a hard shell on their backs. When danger threatens, a snail can slip inside its shell. Slugs and snails are not arthropods but gastropods, which means 'stomach foot', because they seem to slide along on their stomachs. As they crawl along, they ooze a trail of slime to ease their way over the ground.