Insulation
It’s been a hot day, and on this warm evening the bees of Queen Elizabeth’s colony have spread across the front of the hive. This so-called “bearding” (squint at the photo, see the hive door as a mouth with facial hair around it…though the face seems to be upside down in this case) is a reaction to hot weather. Probably the bees cooling off.
Notably, it’s only this one hive that has a beard, and this is the hive without an insulating cork jacket. The other 3 occupied hives have jackets, and no bearding. Maybe a sign that the insulation is effective.