I cannot post a pic here but
About 9PM on May 31st (last night) I walked down to the hive. The air was decidedly cool and I saw this group of bees (about 40 or 50 bees) clustered in and by the entrance. Does anyone know what they were doing? The day before I added a new brood box above this one but I do not know the significance of this or if is important at all.
My guess is you had a warm day and they were just bearding a little at the entrance. :)
Mine do it in the morning but when it warms up they take off and they all go in at night.
Wait until it gets hot and they cover the front of the hive two inches deep. Then you will worry.
PS. They are just sitting out in the cool evening air. Be glad they are strong enough to need to do it.