I spotted this tough caterpillar eating one of my roses the other day in quite frosty conditions. I forgot about it, then spotted it again today and took some photos. It looks like an Angle Shades to me, but I'm not great on larvae-ID. I was struck by what seems to be an inflated anal plate - in fact I thought I was looking at a head for a short while. Is this a defensive adaptation while it is exposed and very vulnerable to hungry birds? Or could it possibly be blister-type damage from an attack. I went out this evening and it has moved round to the underside of the same stem, but is no longer showing the swelling. It's now getting very cold out there so I'll be interested to check it out again tomorrow.
Any ideas what it is...and the nature of the blister/swelling?