Fritillary Caterpillars

Thanks for your help EarlyStages! These do look like a better fit. I'll just leave it as Euphydryas sp. to be on the safe side.

The only thing that I'm not sure about here is that a lot of pictures of Mourning Cloak caterpillars show very pronounced red/brown spots. I guess they may develop with later instars.

Thank you Martin! This beautiful butterfly is found in Spain too, so I think you're probably right. I read that the caterpillars stay together & feed in webbed nests too, so looks like snap! Funnily enough, I've always wanted to see one of the adults, called Camberwell Beauty here in the UK. Having lived around Camberwell where there is a large tiled picture http://commons.wikimedia.org/wiki/File:Camberwell_Beauty_-_geograph.org.uk_-_542877.jpg , and several copies of it around the area, I had long assumed that it had been pushed out of town when it's habitat was destroyed. Turns out there were just a few migrants found in Camberwell long ago and it's never really been a UK native. At least now I've seen the caterpillars!