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'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

Ecology

Aquatic isopods

Common names

United Kingdom

Pill millipedes

Fiction

Gallery

See also

External links

References

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 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 amphibian, 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) ^[1].

Common names

Common names for woodlice vary throughout the English-speaking world. They include: "armadillo bug" ^[2], "cheeselog" (Reading, Berkshire) ^[3], "doodlebug" (also used for the larva of an antlion) ^[4], "pill bug" (usually applied only to the genus ''Armadillidium'') , "roly-poly" ^[5], "potato bug", "roll up bug" ^[6], "slater" ^[7] 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).

Pill millipedes

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.

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.

★ Woodlouse are part of the story in the movie ''Tierra'' by Julio Medem.

★ In the film '', 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.

Gallery

See also

★ Woodlouse hunter spider

External links

★ Woodlice and Pill Bugs - diagnostic photographs

★ BBC nature

★ Video of Woodlouse in motion

References

1. ''Macedonethes stankoi'' n. sp., a rhithral oniscidean isopod (Isopoda: Oniscidea: Trichoniscidae) from Macedonia, Ivo Karaman, , , Organisms Diversity & Evolution, 2003
2. Little armored tanks Bill Amos
3. The sound of Reddin Paul Kerswill
4. "Sow bug"
5. Dialect Survey Bert Vaux & Scott A. Golder
6. You say potato bug, I say roly-poly, you say… Gail Smith-Arrants
7. Guide to New Zealand soil invertebrates: Isopoda Maria Minor & A. W. Robertson

Further reading

★ Catalogue of the terrestrial Isopoda (Crustacea: Isopoda: Oniscidea), Christian Schmidt & Andreas Leistikow, , , Steenstrupia, 2004 (all genera published until end of 2001)