bees fighting

While I was shooting some close up video of a couple of bees on a St. John's Wort blossom I noticed some interaction. When I replayed the scene on my laptop, it was more like a skirmish. One bee actually tried to bite the other one's leg. I'm wondering why some bees get along fine (there's a...

I had some robbing in a nuc the other day, so I made a 3/8" thick "U" shaped shim and covered it with window screen. I tacked it over the entrance as a robbing screen, and the robbing stopped after a day. If you see a lot of frenzied activity, but no fighting at the hive entrance, no bees...