My hive is being robbed yet again. I saw a dead bee on the landing board a few days ago, and didn't think anything of it. Today, I went to do my inspection (last one two weeks ago) and I had robbing going on. I could see the fights and the bees that are robbing are l little bigger then my bees. I covered most of the hive with a wet sheet (that is what I did last time), but left a little part of the entrance uncovered. My bees are defending like crazy, but this is not helping their progress. Does anyone have some really good suggestions on stopping this for good? I got a close up of one of the fights still going on, after I put the sheet on.