Woodlice are small crustaceans that comprise the suborder Oniscidea. These animals live on the soil and feed on leaves, roots and decaying organic materials. They have a rigid, segmented exoskeleton and fourteen legs. More than 3000 species of woodlice are known; common types of woodlice include rock slaters or Ligiidea, pill bugs or Armadillidiidae, sowbugs or Oniscidae and Porcellionidae.
Rock slaters are woodlice members of the family Ligiidae. They have long antennae, larger-than-average compound eyes and some species live in aquatic habitats. The sea slater, or sea roach (Ligia oceanica), widespread along the coasts of Northern Hemisphere, is one of the largest woodlice species, reaching 1.2 inches in length.
Pill bugs, or "roly polies," are woodlice members of the family Armadillidiidae. The common pill bug (Armadillidium vulgare) is a cosmopolitan species found in many habitats around the world. These woodlice can roll into a ball when threatened. Pill bugs are very similar to and often mistaken for pill millipedes, although the two animals are not closely related.
Porcellionidae is a family of woodlice containing more than 500 species which are found on every continent with the exception of Antarctica; these animals cannot roll into a ball as do pill bugs. Often up to 0.8 inches long, the Porcellionidae is grey on its back and paler on the ventral side.The common rough woodlouse (Porcellio scaber) is a common species in this group.
Also called sowbugs, members of the family Oniscidae include several species of woodlice that feed on decomposing organic materials. Commonly found under garden logs and decomposing tree branches, these woodlice prefer humid environments and have brown to black bodies which are generally flatter and shiner than other woodlice. The common shiny woodlouse (Oniscus asellus) is a widespread species in Europe and North America.