I had put a 2-qt mason jar on top of the inner cover with a deep super between the inner and outer covers. The bees have been working cotton, I guess, and didn't mess with the HBH sugar syrup. I've been checking the level every few days and not much action. I checked today and the top of the hive was filled with ants! The bees had propolis-ed up around the edges of the hole in the center of the cover, to keep the ants out. They had left a small bee-sized hole where the guard bees were on duty. As an ant would try to get in, a bee would pop out and sting it, at which point a bunch of ants would attack the bee. I removed the super and brushed the ants off and removed the feeder, put the outer cover back on. I was amazed at how much propolis and burr comb the bees had used to seal the ants out in such a short time. I'm sorry I didn't do a better job of keeping the ants away.