A woodlouse (plural woodlice) is a crustacean from the monophyletic suborder Oniscidea within the isopods. The woodlouse spider ("Dysdera crocata") is a species of spider that preys primarily upon woodlice. Oniscidae is a family of woodlice, including the common woodlouse "Oniscus asellus". Asellus aquaticus is a freshwater crustacean resembling a woodlouse. Woodlouse spiders hunt at night and do not spin webs. The woodlouse has a shell-like exoskeleton, which it must progressively shed as it grows. Metatrichoniscoides celticus is a species of woodlouse in the family Trichoniscidae. "Cylisticus convexus", the "curly woodlouse", has a scattered distribution across the British Isles. A well-known species is the common rough woodlouse, "Porcellio scaber". Other names compare the woodlouse to a pig. Philoscia muscorum, the common striped woodlouse or fast woodlouse, is a common European woodlouse. The woodlouse ("Porcellio scaber") is a particularly common food item. "Metatrichoniscoides celticus" Oliver & Trew, 1981 - A small woodlouse usually below 3mm.