woodlouse

Any of the several families of mostly terrestrial crustaceans of the order Isopoda (especially the sow bugs, genera Onisais and Porcellio) that live in damp places under rocks or fallen timber. They have rounded oval, evenly segmented bodies, flat undersides, and 14 legs. Some species of sow bugs can roll up when threatened. The pillbugs (family Armadillidiidae) typically roll up. Rock slaters (family Ligiidae) are amphibious on ocean beaches.