Vineyard Cleaning Detail

Yesterday, we finished cutting the scions off of the many (6300+) vines that did not make it through the 2013 season so that we could distinguish between the plants that are still remaining (500) when it comes time for pruning next spring.
You might ask, "Why are we keeping dead vines?" and the answer would be:
We are working with our Farm Service Agency (FSA) and have applied for a grant that would provide some financial assistance in replacing our vines. The reason for keeping these dead vines is that they may want to see the devastation.
So, on an unseasonably beautiful day, as we walked the rows lopping as we went along, we came across little green specks on an otherwise dead vine and upon closer inspection, found these:

Apparently, the hole left by the disappearance of the pith is a great home to these little green caterpillars. My husband cut a cane and found 3 of these little fellows huddled there for the winter. All the more reason to do vineyard cleaning!
I haven't figured out what these caterpillars are, but if you know what they might be, please drop me a line!