A Blog for moth recorders in Bucks, Berks and Oxon
Don't know! I suppose the most likely caterpillar of that size to be found now is Angle Shades, which is certainly a possibility although the markings on your specimen look a bit odd. Why don't you try to rear it through?
Steve, if you are on Facebook there is a group called Caterpillars UK and Europe, worth asking on there.
Note: only a member of this blog may post a comment.