A second surprise

Just as I finished the previous blog, I heard loud buzzing from the back.  There was another swarm around the lemon tree.  Then it moved back towards the apiary, hovered over the rose garden and then clustered in the Red Delicious apple tree.

A second swarm on the same day, in October?  My suspicions were aroused, and once I had looked into the nuc, my suspicions were confirmed.  The box was empty save for a couple of bees, three bee corpses and a few rose leaves.  Why did they leave/swarm again?
I have a theory.  I had put them into a "hive" very soon after they had left their mother hive.  Perhaps they were still in a swarming state of mind and therefore were compelled to leave.  As you all may recall, once before I had a captured swarm in a nuc box that left it in short order.  I previously attributed it to my having disturbed them (like a bear), but now that it has happened twice I believe it may have to do with bee behavior.  They may need to have some time clustered before they are ready to move into a new home.  I will write to Professor Seeley to see what he thinks.
In the meantime, I took the frames and feeder away from the nuc box, taped over the hole and put lemongrass oil in a pierce baggie inside and a drop on the porch (in order to make a bait box).  Tomorrow or the day after I'll test my above theory by shaking them into the box once again (assuming they have not move in on their own accord).