Woodlice are small crustaceans—arthropods with a hard, segmented exoskeleton, known as a cuticle, and two pairs of antennae. Woodlice have seven pairs of legs. They live in cool, damp places and eat dead vegetation. Some kinds of woodlouse, known as pill bugs, curl up into an almost perfectly spherical ball when they are threatened.

Spiky yellow

The spiky yellow woodlouse is found only on the tiny island of St Helena in the Atlantic Ocean. It lives high up in the mountains on plants, kinds of tree fern, that grow only on this particular island. There is no other woodlouse like it anywhere else in the world. It is threatened by extinction: by the drying out of its habitat after most of the shady black cabbage trees that kept the undergrowth moist were chopped down, through competition from the accidentally introduced European woodlice, and from being preyed on by the woodlouse spider.