Armadillidium

Armadillidium (/ɑːrmədɪˈlɪdiəm/) is a genus of the small terrestrial crustacean known as the woodlouse. It is one of 18 genera nested within the family Armadillidiidae. Armadillidium is also one of the groups commonly known as pill woodlice, leg pebbles, pill bugs, roly-poly, or potato bugs, and are often confused with pill millipedes such as Glomeris marginata. They are characterised by their ability to roll into a ball ("volvation") when disturbed.

With a penchant for damp and dark places, species in the Armadillidium genus can typically be found under rocks, in leaf litter, and in or around the soil. Aided by their dorsoventrally flattened body and small size – usually growing no bigger than 2.5 cm – these pill bugs are able to squeeze into tight cracks and are common household pests as a result.