Woodlouse
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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.
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[edit] 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.
[edit] 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) [1].
[edit] 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) [2], "roly-poly" [5], "potato bug"[5], "roll up bug" [6], "slater" [7] and "sow bug" [4][5].
[edit] 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).
[edit] 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.
[edit] Gallery
Porcellio scaber and Oniscus asellus - Zalné20070205.jpg
Porcellio scaber (left) and Oniscus asellus (center) |
ArmadillidiumVulgare2.jpg
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Slater rolled up for wiki.jpg
Armadillidium vulgare rolled up |
PhilosciaMuscorum.jpg
Philoscia muscorum |
[edit] See also
[edit] External links
- Woodlice and Pill Bugs - diagnostic photographs
- BBC nature
- Video of Woodlouse in motion
- Growing woodlice in captivity
[edit] References
- ^ Ivo Karaman (2003). Macedonethes stankoi n. sp., a rhithral oniscidean isopod (Isopoda: Oniscidea: Trichoniscidae) from Macedonia. Organisms Diversity & Evolution 3 (8): 1-15.
- ^ a b Bill Amos (2002-08-10). Little armored tanks. Caledonian-Record.
- ^ Paul Kerswill. The sound of Reddin. BBC. Retrieved on 2006-09-17.
- ^ a b "Sow bug". Dictionary.com Unabridged (v 1.0.1) (2006). Retrieved on 2006-09-17.
- ^ a b c Bert Vaux & Scott A. Golder. Dialect Survey. Harvard University. Retrieved on 2006-09-30.
- ^ Gail Smith-Arrants (2004-03-20). You say potato bug, I say roly-poly, you say… (PDF). Charlotte Observer.
- ^ Maria Minor & A. W. Robertson (2006). Guide to New Zealand soil invertebrates: Isopoda. Massey University. Retrieved on 2007-05-13.
[edit] 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)ca:Porquet de Sant Antoni
da:Bænkebider de:Landasseln es:Oniscidea fr:Cloporte io:Aselo lt:Vėdarėliai nl:Landpissebedden ja:ワラジムシ亜目 no:Skrukketroll
nn:Skrukketroll pt:Bicho-da-conta ru:Мокрицы simple:Sow bug
