Oniscus asellus

crustacean

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Last updated

July 1, 2026

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Oniscus asellus is a species of terrestrial crustacean, commonly known as a sow bug or wood louse. It belongs to the order Isopoda and the genus Oniscus.12

This small creature, reaching up to 18 mm (0.7 inches) in length, has an oval, flattened, and arched gray body covered in broad, armor-like plates. It possesses two elbowed antennae that extend about half its body length and seven pairs of limbs. Oniscus asellus is widely distributed in Europe and has been introduced to North America, typically found under stones, in moist leaf litter, and in cellars.1

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sow bug
…especially members of the genus Oniscus. Like the related pill bug, it is sometimes called the wood louse. O. asellus, which grows to a length of 18 mm (0.7 inch), is widely distributed in Europe and has also been introduced into North America. The oval, gray body, which is rather…
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…especially members of the genus Oniscus. Like the related pill bug, it is sometimes called the wood louse. O. asellus, which grows to a length of 18 mm (0.7 inch), is widely distributed in Europe and has also been introduced into North America. The oval, gray body, which is rather…
Read More