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Smithsonian National Museum of Natural History
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Department of Invertebrate Zoology

Armadillidium vulgare

Armadillidium vulgare

Photo Gallery of Terrestrial Isopods


“Pillbugs,” “sowbugs,” “roly-polys,” “potato bugs,” “woodlice.” These are names by which you may know the small isopod crustaceans that live under woodpiles, in leaf litter, under stones, in caves and on the sidewalk. There are more than 4,000 species of terrestrial isopods (Suborder Oniscidea) throughout the world. Many of them are introduced species.

Like all crustaceans, isopods have an exoskeleton and two pairs of antennae. Typically they also have seven pairs of legs, but not always. Terrestrial isopods feed on algae, moss, bark, even decaying plant and animal matter and, like insects, they play a role in the breakdown and recycling of organic nutrients. Cellulose digestion results from the presence of bacteria in the digestive system.

In the U.S. and Canada (excluding Alaska and Hawaii) there are about 120 known species of terrestrial isopods. The most common are widely distributed and have probably been introduced from Europe. A majority of the most abundant species in North America are concentrated in the northeast and northwest, possibly a result of the transport of their ancestors into harbors by human immigrants.

This photo gallery of terrestrial isopods is in progress. New mini-posters will be added as more images of species become available. Each mini-poster is PDF format.* Species currently featured are:

* Either Adobe Acrobat or Adobe Reader is required to open PDF files. If you do not aleady have Adobe Reader, go to for your free download.

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