good video apis, thanks!
one behavior i have witnessed and have happened to catch this a few times myself when divides were not done on a timely basis or queens came in late.
activity i have observed inside the hive prior to an imminent swarm....(no flying activity whatsoever, no pollen or nectar gathering of course) but open the hive to find bees packed solid on the frames, every frame, tight, right next to each other, facing up, and in unison moving side to side with some bees 'piping' and running through or over the tops of their sisters with an elevated hum going on......OOPS......
it's kind of an incredible and amazing sight to see actually, the first time i saw this in the hive, not knowing, and within 2 hours the bees lifted off and away they went into the wild blue yonder......