They swarm onto them, enclosing them in a round “bee ball” and, by vibrating
their flight muscles, heat the inside of the ball to up to 116 degrees Fahrenheit,
a temperature that the hornet can’t survive at (the bees can endure another few).
Just saw this a while ago, while searching the internet for the crazy scary bee that I bravely killed in my house, called a tarantula hawk- google it. Iirc, the bees swarm to 117 f, the hornet cooks then , and the bees can survive to 118. Thought to myself it’s a R avigdor Miller niflaos haborei thingy on steroids.
The bees’ kill point is 5-9 degrees higher according to what I read.