When hornets attack, bees know what to do. A few hundred workers can swarm into balls around hornets and roast them alive with their body heat. The formation of such “hot defensive bee balls” was first described in 1995 in Japanese honeybees . Now we know the defence is something of a kamikaze mission for the bees involved.

When hornets attack a hive to carry off bees to eat, a group of worker bees quickly surround the intruder. The bees vibrate their wing muscles to generate …