Pill woodlouse

Armadillidium vulgare

About

The pill woodlouse is rounded and slate grey, and when it is disturbed, it rolls up into a ball (resembling a small pill) to protect itself. It feeds on dead and decaying matter and is an important nutrient-recycler. It lives in a variety of habitats, but prefers chalk and limestone soils and turf. It emerges at night to feed and can be seen climbing trees and walls in search of mildew and rotting plants to feed on. Woodlice are actually crustaceans, not insects, so are more closely related to crabs and shrimps. They can be very numerous in compost heaps or under rocks in the garden.

How to identify

The pill woodlouse is grey and roundish, with a number of segments or 'plates' in its exoskeleton.

It looks similar to the pill millipede (Glomeris marginata), which also curls up into a ball. The best way to tell the two apart is by counting their legs: woodlice have seven pairs of walking legs, whereas pill millipedes have around 18 pairs. Another difference is that the 'plates' at the rear end of the pill woodlouse are much narrower than those on the rest of the body.

Did you know?

The scientific name of the pill woodlouse, Armadillidium, means 'little armadillo', and refers to the protective 'armour' and rolling behaviour of this species.

How people can help

Our gardens are a vital resource for wildlife, providing corridors of green space between open countryside, allowing species to move about. In fact, the UK's gardens provide more space for nature than all the National Nature Reserves put together. So why not try planting native plants and trees to entice birds, mammals and invertebrates into your backyard? To find out more about encouraging wildlife into your garden, visit our Wild About Gardens website: a joint initiative with the RHS, there's plenty of facts and tips to get you started.