Pill millipedes make up two orders

Pill millipedes make up two orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the resemblance of pill millipedes to certain woodlice, namely the pillbugs of the family Armadillidiidae, also called "potato bugs", or "roly-polies".

Pill millipedes are short compared to other millipedes, with only eleven to thirteen body segments,[2] and are capable of rolling into a ball when disturbed. This ability evolved separately in each of the two orders, making it a case of convergent evolution, rather than homology.[3] Pill millipedes are detritivorous, feeding on decomposing plant matter, usually in woodlands.[4]