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If you’ve ever picked up a flower pot on your patio or dug around in a pile of mulch, you’ve probably seen a roly poly. The common name, given to both pillbugs and sowbugs, is appropriate because of the way they can roll up into a ball—or simply curl up on their side, in the case of sowbugs—as a defense mechanism.
You may be surprised to learn that these critters actually aren’t bugs at all. “They’re isopods, or terrestrial crustaceans, not insects,” says Eric Benson, PhD, professor emeritus and extension entomologist at Clemson University. “They breathe through gills, which is why they are found in damp locations, extracting oxygen from the moisture.”
Mostly, these tiny armored creatures that are related to lobsters and shrimp, are not particularly troublesome for homeowners. “They live under rocks or flower pots or in debris and leaf litter, breaking it down further,” says Faith Oi, PhD, entomologist and extension professor at the University of Florida. “They’re harmless and don’t carry diseases or bite or sting.”
However, their presence sometimes can indicate that you have a moisture problem. “If they come indoors, you may need to do some inspecting,” says Benson. “For example, examine areas where there may be rotting wood, such as where a wooden deck meets the house. Similar to carpenter ants that are attracted to soft, water-damaged wood, pillbugs and sowbugs don’t eat the wood, but they may be there because of leaks and underlying moisture issues.”
Pillbugs (Armadillidium vulgare) and sowbugs (Porcellio laevis)are both commonly called roly poly bugs. They’re grayish and oval, with bodies composed of hardened, overlapping plates, like an armadillo. They reach about ½ to ¾-inch in length. Sowbugs have two tail-like appendages and cannot roll completely into a sphere, while pillbugs have no appendages except antennae and can roll up into a tiny ball, says Benson.
