Thank you, my dears.
To protect themselves during long cold winter months bees are forming a "ball" inside the hive. To generate heat bees vibrate their wing muscles, feeding themselves previously gathered reserve of honey. Inside the ball the temperature never goes down below 25C (77F) - here the queen resides, but on outer surface of it can drop to 10C (50F), or even less. This is critical for single bee life, so they exchange their places from time to time.