I thought this photo is interesting by reason of where the honeybees are pointing their bottoms.
I had just got this swarm into the nucleus box and placed it close to where the swarm was located. The swarm of bees instinctively knew that some of the returning foraging bees might not find their colony in their new home (the nucleus box).
To alert the returning bees, many of the bees congregated on the outside of their new home with their bottoms in the air, emitting pheromones from their nasanov glands. And so, the foraging bees would smell where their friends have gone and safety return to their colony.