Regarding Milt Latham's question:

I can't say what makes bees appear that they might swarm, but were a
swarm imminent, one might try to stop it.  Earlier this Spring a colony
here with a most prolific queen had 25 (medium) frames of brood before
we got weather suitable to split them.  On the first good day I went
with supplies and equipment to do just that.  During preparations for
the split, a tornado of bees formed in the air.  I took a box and a
couple of screened covers and quickly got all the frames with queen
cells into the box.  Apparently word got to the tornado that the queen
they thought was in the hive wasn't, and the tornado coalesced into a
mass on the hive.  I went about my business servicing other colonies.
When that was completed, and the tornado bees were back in their hive, I
added frames with lots of bees to the box, carefully not letting any
bees from the box go back to the hive, and not getting the queen, thus
forming a viable split.  This emergency split was set up in the breeding
yard and now, a few weeks later, has a fine young laying queen.  The old
queen has made up the losses and looks ready to have some brood removed
for addition to other brood to make a new colony. (I don't want to split
again and lose production.) I'm not sure whether such stopping of a
swarm in progress is a reliable procedure, but it did work this time,
and I'm pleased to have the old queen on her old stand.

Bill Morong