AskDefine | Define woodlouse

Word Net

woodlouse n : any of various small terrestrial isopods having a flat elliptical segmented body; found in damp habitats [syn: slater] [also: woodlice (pl)]



  • IPA: /ˈwʊd.ˌlaʊs/
  • SAMPA: /"wUd.%laUs/


woodlouse (plural woodlice)
  1. A terrestrial isopod crustacean (suborder Oniscoidea) with a rigid, segmented exoskeleton, often capable of being rolled into a ball, found in damp, dark places, and feeding only on dead plant matter, usually lives under stones or bark.



Woodlice (known by many common names; see below) are terrestrial crustaceans with a rigid, segmented, calcareous exoskeleton and fourteen jointed limbs. They form the suborder Oniscidea within the order Isopoda, with over 3,000 known species.
Woodlice in the genus Armadillidium can roll up into an almost perfect sphere as a defensive mechanism, hence some of the common names such as pill bug. Most woodlice, however, are not able to do this.


Woodlice need moisture because they breathe through gills, called pseudo trachea, and so are usually found in damp, dark places, such as under rocks and logs. They are usually nocturnal and are detritivores, feeding mostly on dead plant matter. Woodlice then recycle the nutrients back into the soil. In artificial environments such as greenhouses where it can be very moist, woodlice may become abundant and damage young plants, such as ferns.
The woodlouse has a shell-like exoskeleton, which it must progressively shed as it grows. The moult takes place in two stages; 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, who shed their cuticle in a single process.
A female woodlouse will keep fertilized eggs in a patch on the underside of her body until they hatch into small, pink offspring. The mother then appears to "give birth" to her offspring.
Some species of woodlice are able to roll into a ball-like form when threatened by predators, leaving only their armoured back exposed. This ability, or dominant behavior, explains many of the woodlouse's common names.
Metabolic rate is temperature dependent in woodlice. In contrast to mammals and birds, invertebrates are not "self heating": the external environmental temperature relates directly to their rate of respiration.
They are not generally regarded as a serious household pest as they do not spread disease and do not damage wood or structures, however their presence can indicate damp problems.

Aquatic isopods

Although woodlice are terrestrial crustaceans, several forms have returned to water. Although most of these are amphibious, some have become truly aquatic.
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) .

Common names

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.
Names include: "armadillo bug" , "cheeselog" (Reading, Berkshire) , "doodlebug" (also used for the larva of an antlion) , "pill bug" (usually applied only to the genus Armadillidium) , "potato bug", "slater" , "Carpenter", "Wood Bug", and "sow bug" 
In Altona, Victoria, Australia. A woodlouse is referred to as a "Butchie Boy", or "Butcher Boy", or "Slater Bug".

United Kingdom

There are 37 native or naturalised species in the United Kingdom, ranging in colour and in size (3–30 mm) of which 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). They are also called "wood bugs" and "slaters" in some areas.

Pillbugs and pill millipedes

Pillbugs (woodlice of the family Armadillidiidae) can be confused with Pill millipedes although they are only very distantly related to one another.
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. Both 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 also have thirteen body segments, whereas the woodlouse has eleven. In addition, pill millipedes are smoother, and resemble normal millipedes in overall coloring and the shape of the segments.


image:ArmadillidiumVulgare2.jpg|Armadillidium vulgare image:PhilosciaMuscorum.jpg|Philoscia muscorum


  • In the webcomic Wigu, giant woodlice ("slagathors") are infrequently featured. They are forced to run organised races on alien planets.
  • The Gustav, a mecha from the Zoids franchise, is similar in design to a woodlouse.
  • In a Rugrats episode, Chuckie Finster kept one as a pet, but it died a few days after. Its name was Melville.
  • In Salad Fingers (an underground cartoon by David Firth) there was a woodlouse which was tragically flattened when Salad Fingers tried to pet her.
  • In Lexx, the Gigashadow resembles a gigantic, planet-sized woodlouse. The Lexx logo resembles a rolled-up woodlouse as well.
  • In Rescue Rangers'', Professor Nimnul uses his Giganto Gun to turn pillbugs into fake aliens for extorting gold as spaceship fuel.
  • In the 1980s British vet-based television drama "One by One" a character visited a veterinary surgery with a pet armadillo after concerns the animal had given birth. On inspection, these were not juvenile armadillos - but simply woodlice in the animal's cage.


Further reading

  • ">}} (all genera published until end of 2001)
woodlouse in Catalan: Porquet de Sant Antoni
woodlouse in Danish: Bænkebider
woodlouse in German: Landasseln
woodlouse in Spanish: Oniscidea
woodlouse in French: Cloporte
woodlouse in Ido: Aselo
woodlouse in Lithuanian: Vėdarėliai
woodlouse in Dutch: Landpissebedden
woodlouse in Japanese: ワラジムシ亜目
woodlouse in Norwegian: Skrukketroll
woodlouse in Norwegian Nynorsk: Skrukketroll
woodlouse in Portuguese: Bicho-da-conta
woodlouse in Russian: Мокрицы
woodlouse in Simple English: Sow bug
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