Another apt name for these are “thousand-leggers.” There are about 8,000 described species of millipedes. Their choice of food is decaying material. They are born with only 3 pairs of legs; they attain their numerous appendages and body segments with each molt.
Millipede – Julidae family

Millipedes have a defense mechanism involving a nasty smelling chemical that oozes from each body segment. Their head segment does not have these glands, which explains why they coil up when in their defensive position. But if the head is attacked first and/or removed by a predator, then there is easy access to the rest of the millipede.
For more info:
Bug Guide