pill bug

any of various small terrestrial isopods, esp. of the genera Armadillidium and Oniscus, which can roll themselves up into a spherical shape.

[1835-45, Amer.]

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Any species of terrestrial crustacean in the genera Armadillidium and Armadillo (both in the order Isopoda), native to Europe and introduced worldwide.

Pill bugs (sometimes called wood lice) resemble tiny armadillos in appearance and behaviour; they have a gray, oval body covered with platelike armour and, when disturbed, roll into a ball. They are about 0.75 in. (19 mm) long. Pill bugs live in dry, sunny places, in dry leaf litter, and on forest edges. See also sow bug.

Pill bugs (Armadillidium vulgare)

E.S. Ross

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▪ crustacean

 any of the terrestrial crustaceans of the families Armadillididae and Armadillidae (order Isopoda). When disturbed, the pill bug rolls itself up into a tiny ball. Like the related sow bug (q.v.), it is sometimes called the wood louse. For mollusks also known as pill bugs, see chiton.

      The common pill bug Armadillidium vulgare (family Armadillididae) is about 17 millimetres (0.7 inch) long. The gray body, with its platelike segments, somewhat resembles a miniature armadillo, an armoured mammal that also curls into a ball when disturbed. A. vulgare occurs in dry, sunny places, in leaf litter, and on the edges of wooded areas. Originally found in Europe, it now occurs worldwide. A. nasatum, native to northern Europe, has been introduced into North America. Armadillo officinalis (family Armadillidae), which attains lengths of 19 millimetres (0.75 inch), is native to southern Europe.

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