What catapillar is this?

[Bun]

Sorry, no pic.
Near to where my husband works there is a bank of some kind of ground covering cotoneaster. Every year it gets covered in, what I always thought looked like heavy duty spiders webs. *shudder* I had a closer look yesterday & saw hundreds of catapillars in them! They were quite short, dark & had 2 orange spots on their backs.
Any clues?  ???

[Bun]

[h2yoho]

Seen loads of those Bun, and would like to know too.  :-\