When I cracked open the inner cover on this hive to feed them today, a lot of the bees threw their abdomens up and exposed their stings as a warning. It didn't take long for the warning to turn to action, and they started launching at me. Luckily I was wearing a veil, which spared me from numerous stings. This hive has been uncharacteristically defensive the last couple times I've been in it; hopefully it's not a sign of a failed queen. I don't want to pull frames to check for her right now due to the cold weather, so I'll do what I can to keep them fed and comfortable until I can get into the brood chamber next spring.