I can't believe they're not butterflies

Apparently overnight this week some bushes near us became absolutely covered in cobwebs. Went to take a look today and the webs were supporting thousands of little catterpillars.

Spent ages taking various photos and then apologising to an interested crowd of local dog-walkers who seemed to think I must be some sort of insect expert. I had to explain that, although I was interested enough to point a camera at the phenomenon I had no idea what caused it.