Woodlouse

Common names for woodlice vary throughout the English-speaking world. A number of common names make reference to the fact that some species of woodlice can roll up into a ball. Other names compare the woodlouse to a pig.

Common names include:

• "armadillo bug"[7]
• "billy baker" (South Somerset)
• Billy Button (Dorset)
• "boat-builder" (Newfoundland, Canada)[8]
• "butcher boy" or "butchy boy" (Australia,[9] mostly around Melbourne[10])
• "carpenter" or "cafner" (Newfoundland and Labrador, Canada)[11]
• "carpet shrimp" (Ryedale)
• "charlie pig" (Norfolk, England)
• "cheeselog" (Reading, England)[12]
• "cheesy bobs" (Guildford, England)[13]
• "cheesy bug" (North West Kent, England)[14]
• "cheesey wig"
• "chiggy pig" (Devon, England)[15][16]
• "chucky pig" (Devon, Gloucestershire, Herefordshire, England)[17]
• "chuggy peg" (North Devon)
• "crawley baker" (Dorset)
• "daddy grampher" (North Somerset)
• "damp beetle" (North East England)
• "dandy postman" (Essex and East London)
• "doodlebug" (also used for the larva of an antlion)[18]
• "gramersow" (Cornwall, England)[19]
• "granny grey" (South Wales)[20]
• "granny grunter" (Isle of Man)
• "hog-louse"[21]
• "horton bug" (Deal, Kent, England)
• "humidity bug" (Ontario, Canada)
• "menace" (Plymouth, Devon)
• "monkey-peas" (Kent, England)[14]
• "monk's louse" (transl. "munkelus", Norway)[22]
• "parson's pig" (Isle of Man)[23]
• "pea bug" or "peasie-bug" (Kent, England)[14]
• "piggy wig"
• "pill bug" (usually applied only to the genus Armadillidium)[24]
• "piss-the-bed" (Netherlands)
• "potato bug"[25]
• "roll up bug"[26]
• "roly-poly"[25]
• "rosary bug" (Turkey)
• "slater" (Scotland, Ulster, New Zealand and Australia)[27][28][29]
• "sow bug"[30]
• "wood bug" (British Columbia, Canada)[31]
• "wood-louse"

Basic body regions of the woodlouse

The woodlouse has a shell-like exoskeleton, which it must progressively shed as it grows. The moult takes place in two stages;[32] the back half is lost first, followed two or three days later by the front. This method of moulting is different from that of most arthropods, which shed their cuticle in a single process.

A female woodlouse will keep fertilised eggs in a marsupium on the underside of her body, which covers the under surface of the thorax and is formed by overlapping plates attached to the bases of the first five pairs of legs. They hatch into offspring that look like small white woodlice curled up in balls, although initially without the last pair of legs.[32] The mother then appears to "give birth" to her offspring. Females are also capable of reproducing asexually. [33]

Despite being crustaceans like lobsters or crabs, woodlice are said to have an unpleasant taste similar to "strong urine".[33]

Comparison of the pill bug Armadillidium vulgare (left) and the pill millipede Glomeris marginata (right)

Pillbugs (woodlice of the family Armadillidiidae, also known as pill woodlice) can be confused with pill millipedes of the order Glomerida.[34] Both of these groups of terrestrial segmented arthropods are about the same size. They live in very similar habitats, and they can both roll up into a ball. Pill millipedes and pillbugs appear superficially similar to the naked eye. This is an example of convergent evolution.

Pill millipedes can be distinguished from woodlice on the basis of having two pairs of legs per body segment instead of one pair like all isopods. Pill millipedes have 12 to 13 body segments and about 18 pairs of legs, whereas woodlice have 11 segments and only seven pairs of legs. In addition, pill millipedes are smoother, and resemble normal millipedes in overall colouring and the shape of the segments.

Woodlouse under a concrete block.

Environmental extremes

Hemilepistus reaumuri lives in "the driest habitat conquered by any species of crustacean".

Ligia oceanica is aquatic.

Many members of Oniscidea live in terrestrial, non-aquatic environments, breathing through trachea-like lungs in their paddle-shaped hind legs (pleopods), called pleopodal lungs. Woodlice need moisture because they rapidly lose water by excretion and through their cuticle, and so are usually found in damp, dark places, such as under rocks and logs, although one species, the desert dwelling Hemilepistus reaumuri, inhabits "the driest habitat conquered by any species of crustacean".[35] They are usually nocturnal and are detritivores, feeding mostly on dead plant matter.

A few woodlice have returned to water. Evolutionary ancient species are amphibious, such as the marine-intertidal sea slater (Ligia oceanica), which belongs to family Ligiidae. Other examples include some Haloniscus species from Australia (family Scyphacidae), and in the northern hemisphere several species of Trichoniscidae and Thailandoniscus annae (family Styloniscidae). Species for which aquatic life is assumed include Typhlotricholigoides aquaticus (Mexico) and Cantabroniscus primitivus (Spain).[36]

Woodlice are the most common prey of the spider Dysdera crocata.

Woodlice are eaten by a wide range of insectivores, including spiders of the genus Dysdera, such as the woodlouse spider Dysdera crocata,[30] and land planarians of the genus Luteostriata, such as Luteostriata abundans.[37]

Although woodlice, like earthworms, are generally considered beneficial in gardens for their role in controlling pests,[38] producing compost and overturning the soil, they have also been known to feed on cultivated plants, such as ripening strawberries and tender seedlings.[39]

Woodlice can also invade homes en masse in search of moisture and their presence can indicate dampness problems.[40] They are not generally regarded as a serious household pest as they do not spread malady and do not damage sound wood or structures. They can be easily removed with the help of vacuum cleaners, chemical sprays, insect repellents, and insect killers.[41]

There are over 45 native or naturalised species of woodlouse in the British Isles, ranging in colour and in size (3–30 millimetres or 0.1–1.2 inches). Of these 45 species, only five are common: Oniscus asellus (the common shiny woodlouse), Porcellio scaber (the common rough woodlouse), Philoscia muscorum (the common striped woodlouse), Trichoniscus pusillus (the common pygmy woodlouse), and Armadillidium vulgare (the common pill bug).

• Media related to Oniscidea at Wikimedia Commons
• Data related to Oniscidea at Wikispecies

• Helmut Schmalfuss (2003). "World catalog of terrestrial isopods (Isopoda: Oniscidea)—revised and updated version" (PDF). Stuttgarter Beiträge zur Naturkunde, Serie A. 654: 341 pp. (lists all validated species of Oniscidea published up to the end of 2004)
• Helmut Schmalfuss; Karin Wolf-Schwenninger (2002). "A bibliography of terrestrial isopods (Crustacea, Isopoda, Oniscidea)—revised and updated version" (PDF). Stuttgarter Beiträge zur Naturkunde, Serie A. 639: 120 pp. (lists most scientific publications on the biology of Oniscidea published in a European language until the year 2004.)
• Christian Schmidt & Andreas Leistikow (2004). "Catalogue of the terrestrial Isopoda (Crustacea: Isopoda: Oniscidea)" (PDF). Steenstrupia. 28 (1): 1–118. (lists all genera published up to the end of 2001)