Woodlouse

A woodlouse, also known as a pill bug (Armadillidium only), armadillo bug, sow bug or slater is a terrestrial crustacean with a rigid, segmented, calcareous exoskeleton and fourteen jointed limbs. They need moisture and so are usually found in damp, dark places, such as under rocks and logs. They are usually nocturnal and are detritovores, feeding only on dead plant matter.

They belong to the order Isopoda, suborder Oniscidea, with over 3000 known species.

In Britain there are 37 native or naturalized species ranging in colour and in size (3 - 30 mm) of which only five are common - Oniscus asellus (Common shiny woodlouse), Porcellio scaber (Common rough woodlouse), Philoscia muscorum (Common striped woodlouse), Trichoniscus pusillus (Common pygmy woodlouse) and Armadillidium vulgare (Common pill bug).