This is the third time I have witnessed what appears to be a small swarm entering my established hives. I have not heard of this happening to anyone else so I'm trying to find out whats going on. they have been between softball to cantaloupe size and appear to enter the hive without struggle. They explore all openings of the hive as I would expect from robbers or a foreign swarm. but than 10 min later it is business as usual at the entrance. My queens is marked and to my surprise every time this has happened the next day when I make an inspection the same queen is there. I thought i understood robbing and swarming but this does not seem to be either. Any idea whats going on?