Update: We have identified these as BROWN MARMORATED STINK BUGS (first and second instars?)! See pictures here, here and here for comparison. We actually killed these bugs after we took these pictures and it’s a good thing because brown marmorated stink bugs are apparently an invasive pest.
We saw these bugs congregating on a grape leaf. We thought they were planning some sort of invasion until we saw the eggs in our pictures. They were barely visible to the naked eye. We have searched high and low on websites for grape pests and other bugs and haven’t been able to definitively identify these guys. So, if you know what they are, do share!
For more information on brown marmorated sink bugs in grapes and wine: http://www.goodfruit.com/good-to-know-4/