Woodlouse

Woodlice
Oniscus asellus
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Order: Isopoda Suborder: Oniscidea Latreille, 1802
Infraorders and Families
Infraorder Tylomorpha Tylidae Infraorder Ligiamorpha Superfamily Trichoniscoidea Buddelundiellidae Trichoniscidae Superfamily Styloniscoidea Schoebliidae Styloniscidae Titaniidae Tunanoniscidae Superfamily Oniscoidea Bathytropidae Berytoniscidae Detonidae Halophilosciidae Olibrinidae Oniscidae Philosciidae Platyarthridae Pudeoniscidae Rhyscotidae Scyphacidae Speleoniscidae Sphaeroniscidae Stenoniscidae Tendosphaeridae Superfamily Armadilloidea Actaeciidae Armadillidae Armadillidiidae Atlantidiidae Balloniscidae Cylisticidae Eubelidae Periscyphicidae Porcellionidae Trachelipodidae incertae sedis (Ligiamorpha) Dubioniscidae Hekelidae Irmaosidae Pseudarmadillidae Scleropactidae Ligiidae Mesoniscidae

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.

Contents 1 Ecology 2 Aquatic isopods 3 Common names 4 United Kingdom 5 Pill millipedes 6 Gallery 7 Fiction 8 See also 9 External links 10 References 11 Further reading

Ecology

Woodlice need moisture because they breathe through gills, called pseudotrachea, 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.

They have a shell-like exoskeleton. As the woodlouse grows, it must progressively shed this shell. The moult takes place in two stages; the back half is lost first, followed two or three days later by the front. Woodlice are the only arthropods to moult in this way, with all others shedding their cuticle in a single process.

A female woodlouse will keep fertilised 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 dampness 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) Ivo Karaman (2003). Macedonethes stankoi n. sp., a rhithral oniscidean isopod (Isopoda: Oniscidea: Trichoniscidae) from Macedonia. Organisms Diversity & Evolution 3 (8): 1-15. .

Common names

Common names for woodlice vary throughout the English-speaking world. They include: "armadillo bug" Bill Amos (2002-08-10). Little armored tanks. Caledonian-Record., "cheeselog" (Reading, Berkshire) Paul Kerswill. The sound of Reddin. BBC. Retrieved on 2006-09-17., "doodlebug" (also used for the larva of an antlion) "Sow bug". Dictionary.com Unabridged (v 1.0.1) (2006). Retrieved on 2006-09-17., "pill bug" (usually applied only to the genus Armadillidium) , "roly-poly" Bert Vaux & Scott A. Golder. Dialect Survey. Harvard University. Retrieved on 2006-09-30., "potato bug", "roll up bug" Gail Smith-Arrants (2004-03-20). You say potato bug, I say roly-poly, you say… (PDF). Charlotte Observer., "slater" Maria Minor & A. W. Robertson (2006). Guide to New Zealand soil invertebrates: Isopoda. Massey University. Retrieved on 2007-05-13. and "sow 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.

Pill millipedes

A comparison of the pill millipede Glomeris marginata and isopod Armadillidium

Pill millipedes are often confused with pillbugs (woodlice of the family Armadillidiidae). This is an example of parallel evolution, and pill millipedes can be distinguished from woodlice in several ways, especially that they have two pairs of legs per body segment, instead of one pair like isopods. They also have thirteen body segments rather than eleven, and they are smoother, more like those of normal millipedes in color and style.

Gallery

Porcellio scaber and Oniscus asellus - Zalné20070205.jpg Porcellio scaber (left) and Oniscus asellus (center)

ArmadillidiumVulgare2.jpg Armadillidium vulgare

Slater rolled up for wiki.jpg Armadillidium vulgare rolled up

Philoscia muscorum

Fiction

• In To Kill a Mockingbird, the main character Scout pokes a "roly-poly".

• In the Pixar film A Bug\'s Life two supporting characters are acrobatic woodlice, "Tuck" and "Roll", who have their own ride at Disney\'s California Adventure Park.

• The giant creatures called Ohmu in Hayao Miyazaki\'s Nausicaä of the Valley of the Wind also resemble woodlice.

• 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 Harry Potter and Order of the Phoenix, woodlice are fed to bowtruckles.

• Dink Smallwood includes the woodlouse as an enemy.

• 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.

• Woodlice are part of the story in the movie Tierra by Julio Medem.

• In the film La métamorphose des cloportes, woodlice (cloportes) are a part of the title, and shots of woodlice appear during the opening credits.

• In Lexx, the Gigashadow resembles a gigantic, planet-sized woodlouse. The Lexx logo resembles a rolled-up woodlouse as well.

• In Rescue Rangers, Professor Nimnal uses his Giganto Gun to turn pillbugs in to fake aliens for extorting gold as spaceship fuel.

See also

• Woodlouse hunter spider

External links

• Woodlice and Pill Bugs - diagnostic photographs
• BBC nature
• Video of Woodlouse in motion
• Growing woodlice in captivity

References

Further reading

• Christian Schmidt & Andreas Leistikow (2004). Catalogue of the terrestrial Isopoda (Crustacea: Isopoda: Oniscidea). Steenstrupia 28 (1): 1-118.  (all genera published until end of 2001)

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