Pill Bug or Wood Louse or Sow Bug...

These little crustaceans go by a lot of names. This looks like the common wood louse to me (Oniscus asellus). I've always called them wood louse but I quite like the name Pill Bug - maybe because they roll up like a (spherical) pill??

All these photos are of the same one: a female; she was holding eggs in the pouch on her underside.

Great little armadillo

She was in our compost bin. Wood lice are good for compost bins and very welcome as they eat a lot of cellulose which is normally slower to break down. 

It doesn't take much to make them roll up in a ball.

Unrolling isn't always so smooth..!