Common Crustaceans: Pillbugs and Sowbugs

Often times the most amazing discoveries can be made in one’s own backyard. Take, for example, pillbugs and sowbugs. These are the little, grey, “armored” critters you commonly encounter if you turn over a rock, a piece of rotting wood, or a pile of decaying leaves, especially in damp areas. When revealed, you may have seen them curl into a tiny ball, or scurry away on several pairs of legs. Although they live on land, and may look like insects when only given a cursory glance, these animals are actually crustaceans, and have gills!

When we think of crustaceans, the aquatic types probably come to mind first – shrimp, lobsters, and crabs. But pillbugs and sowbugs are crustaceans too. This means they’re more closely related to lobsters and shrimp than to bees and ants. (Crustaceans belong to a larger group of animals, the arthropods, which also includes insects, spiders, and others.) Pillbugs (which can roll into a ball) and sowbugs (which can’t) have had very successful lives on land, as there are now about 4,000 species of these critters, living just about anywhere from beaches to deserts.

The member of this group that we encounter most frequently is the common pillbug or roly poly (Aramadillidium vulgare). It used to only live in southern Europe, but was spread throughout Europe and then to North America by people. Without any native species in North America, it’s flourished here! Wherever they go, these little critters play a big, important role– they eat decaying material, like plants and even dead animals, and through this process help recycle nutrients in the soil.

So, if you’re looking for a short-lived pet, you may want to consider a pillbug or sowbug – they take up little space, don’t eat expensive food, and live up to about three years! And, if one looks closely, it’s possible to find different coloration patterns on these tiny crustaceans, making that a possible feature of distinction and interest.

For further reading:

• The University of Arizona’s webpage “Isopod, Pillbug, Sow Bug Information”
• M. A. Alikhan’s book Terrestrial Isopod Biology
• Teisha Rowland’s article “From Roly Polies to Praying Mantises” in the Santa Barbara Independent
• Carolina Biological Supply Company’s webpage “Terrestrial Isopods (Pill Bugs/Sow Bugs)“