A particularly attractive woodlouse. Fully grown it reaches about 12 mm long. It has a black head, black eyes, and a dark central stripe with a row of yellow blotches down either side. Antennae with two flagellal segments. 

 Philoscia muscorum (Common Striped Woodlouse) also has a dark central band but has a 'stepped' outline, unlike the smoother outline of Porcellio spinicornis.

ID Guide to Common Woodlice

It is common in gardens where it likes mortared walls.

All year round.

It can run quite fast, but usually stays still for a while when first disturbed.

Widespread and locally common in Britain.

Common in Leicestershire and Rutland.