Science, Tech, Math › Animals & Nature 15 Fascinating Facts About Pill Bugs Share Flipboard Email Print Paul Starosta/Getty Images Animals & Nature Insects Behavior & Communication Basics Ants. Bees, & Wasps Beetles Butterflies & Moths Spiders Ticks & Mites True Bugs, Aphids, Cicadas, and Hoppers Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Marine Life Forestry Dinosaurs Evolution View More By Debbie Hadley Entomology Expert B.A., Political Science, Rutgers University Debbie Hadley is a science educator with 25 years of experience who has written on science topics for over a decade. our editorial process Debbie Hadley Updated December 12, 2019 The pill bug goes by many names—roly-poly, woodlouse, armadillo bug, potato bug, but whatever you call it, it's a fascinating creature—or actually 4,000 species of creature. The nocturnal crustaceans have seven pairs of legs, segmented sections like a lobster's tail, and prefer humid environments. They eat rotting vegetation and help nutrients in it get returned to the soil for plants to feed on, so they're not pests. They don't bother living vegetation. These insights into pill bugs will give you a newfound respect for the tiny tank living beneath your flower pots. 01 of 15 Pill Bugs Are Crustaceans, Not Insects Though they're often associated with insects and are referred to as "bugs," pill bugs actually belong to the subphylum Crustacea. They're much more closely related to shrimp and crayfish than to any kind of insect. 02 of 15 Pill Bugs Breathe Through Gills Like their marine cousins, terrestrial pill bugs use gill-like structures to exchange gases. They require moist environments to breathe but cannot survive being submerged in water. 03 of 15 A Juvenile Pill Bug Molts in 2 Sections Like all arthropods, pill bugs grow by molting a hard exoskeleton. But pill bugs don't shed their cuticle all at once. First, the back half of its exoskeleton splits away and slides off. A few days later, the pill bug sheds the front section. If you find a pill bug that's gray or brown on one end, and pink on the other, it's in the middle of molting. 04 of 15 Mothers Carry Their Eggs in a Pouch Like crabs and other crustaceans, pill bugs tote their eggs around with them. Overlapping thoracic plates form a special pouch, called a marsupium, on the pill bug's underside. Upon hatching, the tiny juvenile pill bugs remain in the pouch for several days before leaving to explore the world on their own. 05 of 15 Pill Bugs Don't Urinate Most animals must convert their wastes, which are high in ammonia, into urea before it can be excreted from the body. But pill bugs have an amazing ability to tolerate ammonia gas, which they can pass directly through their exoskeleton, so there's no need for them to urinate. 06 of 15 A Pill Bug Can Drink With Its Anus Though pill bugs do drink the old-fashioned way—with their mouthparts—they can also take in water through their rear ends. Special tube-shaped structures called uropods can wick water up when needed. 07 of 15 Some Species Curl Into a Ball When Threatened Most kids have poked a pill bug to watch it roll up into a tight ball. In fact, many people call them roly-polies for just this reason. Their ability to curl up distinguishes the pill bug from another close relative, the sowbug. 08 of 15 Pill Bugs Eat Their Own Poop Yes indeed, pill bugs munch on lots of feces, including their own. Each time a pill bug poops, it loses a little copper, an essential element it needs to live. To recycle this precious resource, the pill bug will consume its own poop, a practice known as coprophagy. 09 of 15 Sick Pill Bugs Turn Bright Blue Like other animals, pill bugs can contract viral infections. If you find a pill bug that looks bright blue or purple, it's a sign of an iridovirus. Reflected light from the virus causes the cyan color. 10 of 15 A Pill Bug's Blood Is Blue Many crustaceans, pill bugs included, have hemocyanin in their blood. Unlike hemoglobin, which contains iron, hemocyanin contains copper ions. When oxygenated, pill bug blood appears blue. 11 of 15 They 'Eat' Metals Pill bugs are important for ridding the soil of heavy metal ions by taking in copper, zinc, lead, arsenic, and cadmium, which they crystallize in their midgut. Thus, they can survive in contaminated soil where other species can't. 12 of 15 They're the Only Land Crustacean Pill bugs represent the only crustacean that has widely colonized the land. They're still a bit "fish out of water," though, as they are at risk of drying out on land; they haven't developed the waterproof waxy coating of arachnids or insects. Pill bugs can survive until they get down to 30 percent dry. 13 of 15 They're Humidity Sponges If the humidity gets really high in the atmosphere, above 87 percent, pill bugs can absorb moisture from the air to stay hydrated or improve their hydration. 14 of 15 They're European Imports Pill bugs probably came to North America with the lumber trade. European species may have originated in the Mediterranean region, which would explain why they don't survive winters where it gets below 20 degrees F as they aren't underground burrowers. 15 of 15 Babies Don't Have All Their Legs When born, pill bug young have only six pairs of legs. They get the seventh pair following their first molt.