I had 4 hives to die out over the winter. I went out today to spray the comb with bt to keep the wax moths out. There were robber bees cleaning them out, but as foragers, they do not sting, so I ignored them and kept spraying.
As I separated the boxes of the last hive, they began to attack. One sting on the leg, 3 on the belly, one on the head, told me quickly that this hive isn't a deadout. Only a live colony protecting it's hive would do that.
So, I've got one more hive than I thought I had.