Porcellio scaber

Porcellio scaber (otherwise known as the common rough woodlouse or simply rough woodlouse), is a species of woodlouse native to Europe but with a cosmopolitan distribution. They are often found in large numbers in most regions, with many species (shrews, centipedes, toads, spiders and even some birds) preying on them. P. scaber is found across Central and Western Europe. In the United Kingdom, it is one of the 'big five' species of woodlice. It has also colonised North America, South Africa and other regions including the remote sub-Antarctic Marion island, largely through human activity. It is also the most common species of woodlice found in Australia. P. scaber has an oval body, can grow up to 20 millimetres (0.79 in) long, and is usually a grey colour, paler underneath, although brown, blue, yellow, or pinkish hues may also be observed (like many other woodlice, a red variety can often be found in coastal areas). The dorsal (upper) surface of its segmented exoskeleton is covered in a series of small tubercles hence its common name. At the head it has two pairs of antennae, with the inner pair being very small. Two compound eyes are located on the dorsal side of the head, while the mouth parts are on the ventral (lower) side. There are 7 pairs of legs, corresponding to the 7 segments of the thorax. The short abdomen consists of 6 segments. On the ventral side of the abdomen there are two whitish pseudo-lungs, connected with pores to the outside air. At the rear end there are is a small telson flanked by a pair of appendages known as uropods. P. scaber loses water by diffusion through its permeable exoskeleton which lacks a waxy cuticle. Because of this, to avoid desiccation, it often seeks out environments with humid air and plenty of ground moisture, preferably cold to minimize rate of water loss, and dark to avoid detection by predators. It lives in a wide variety of damp habitats but it is less dependent on high levels of humidity than Oniscus asellus. P. scaber is a detritivore - it mainly feeds on decaying leaf litter but will consume any rotting plant matter. Living plants are of limited nutritional value for these woodlice which prefer to feed on the bacteria and fungi which cause decay. P. scaber has very sensitive olfactory receptors that allow it detect the smell of microbial activity and so locate food. This ability to quickly detect the faintest sign of decay has led to the false belief that they harm seedlings and soft fruit. 25 to 90 fertilized eggs and the larvae are carried by the mother in a fluid-filled sac at the ventral side of the abdomen for about 40-50 days. The young are fully grown after 3 months; the adult animals have a life expectancy of about two years.