Should I move my similar example below as well?

but then I saw that you had never actually said what the host plant was. If it's raspberry or blackberry, then I'd say go ahead, but if not, it might be something else.
[edit] I now see that that was discussed below... I'm not sure, the leaf venation doesn't look right to me, and sort of reminds me of a sugar maple leaf (that's just a gut reaction; I haven't actually looked at other photos to compare). It does seem to actually be feeding on that leaf, so if it isn't Rubus, that would seem to indicate another ID for the larva.

Hi Steve, do you have a photo that shows a larger view of the whole leaf, perhaps the uncropped original? If so, post it and we'll try to identify the plant species.

I added a second image which has a wider view though I'm not sure it helps.

I see that it has a slightly toothed margin, but I still cannot make out what it is :( . My Rubus expert said "Nothing comes to mind right away - the leaf margin doesn't look like any Rubus that I'm accustomed to."

Looks very similar. Was it on Blackberry too?

But there was a lot of Blackberry in the area.

Raspberry Sawfly - Monophadnoides geniculatus

Nice job! Because of your observation, I googled sawfly and Blackberry and then Rasberry and found an image here.

This larva belongs to the species Priophorus brullei http://bugguide.net/node/view/350571/bgimage .
This species feeds on Raspberry, Blackberry and Rowan (Sorbus aucuparia).