Armadillidium

Armadillidium
An Armadillidium granulatum in its roll-up stages.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Isopoda
Suborder:	Oniscidea
Family:	Armadillidiidae
Genus:	Armadillidium Brandt, 1833
Diversity
189 species

Armadillidium (/ɑːrmədɪˈlɪdiəm/) is a genus of the small terrestrial crustacean known as the woodlouse. Armadillidium are also commonly known as pill woodlice, leg pebbles, pill bugs, roly-poly, or potato bugs, and are often confused with pill millipedes such as Glomeris marginata. They are characterised by their ability to roll into a ball ("volvation") when disturbed.

They chiefly feed on decaying organic matter like leaves, decomposed wood fibers, and less so on other organic material like lichens. They are usually found in moist areas such as decomposing leaf matter and soil. Armadillidium vulgare is the most abundant species in Europe and has been introduced worldwide. However, the vast majority of species are endemic to small regions close to the Mediterranean Sea, in much lower numbers than common species such as A. vulgare, and hence are understudied.

Unlike other terrestrial arthropods such as insects and spiders, pill bugs do not have a waxy cuticle that would reduce evaporation from their bodies. Pill bugs also use modified lungs, called pseudotrachea, for respiration, and the lungs must remain moist to function. Individual pill bugs typically live for two or three years, and females brood eggs once or twice each summer. In larger species and individuals, up to over an hundred eggs are brooded at a time in the marsupium, a pocket on the ventral side of the female pill bug. The marsupium provides nutrients and oxygen to the eggs until the hatch, resulting in a sort of “live birth”.

The colouration especially of young A. klugii resembles the red hourglass marking of the Mediterranean black widow Latrodectus tredecimguttatus. This is probably a kind of mimicry, to ward off predators that mistake the harmless animal for a venomous spider.^[1]

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  Armadillidium depressum
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  Armadillidium granulatum
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  Armadillidium lagrecai
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  Armadillidium pictum
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  Armadillidium pulchellum
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  Armadillidium vulgare
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  Armadillidium nasatum
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  Macro shot of an Armadillidium opacum
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  Armadillidium gestroi
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  Armadillidium pallasii
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  Armadillidium versicolor
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  Armadillidium album
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  Armadillidium atticum
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  Armadillidium marmoratum

There are 189 recognised species in the genus Armadillidium:^[2][3]

• Johann Friedrich von Brandt
• Karl Wilhelm Verhoeff

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