Bill Oddie and John Waters go in search of a rare British beetle - the blue ground beetle. It is found under moss on trees, and only lives in seven forests in Devon and Cornwall. They catch one in a specimen jar and admire its beautiful dark blue carapace. Blue beetles have an interesting defence system - they squirt acid from their abdomens this wouldn't be too good if you got it in the eye. They follow the slime trails of slugs and use their very large jaws to grab the victim before injecting it with digestive juices.They can eat a whole slug in half an hour.