Honeybee mobs overpower hornets

Honeybee hordes use two weapons - heat and carbon dioxide - to kill their natural enemies, giant hornets.

Japanese honeybees form "bee balls" - mobbing and smothering the predators.

This has previously been referred to as "heat-balling", but a study has now shown that carbon dioxide also plays a role in its lethal effectiveness.

In the journal Naturwissenschaften, the scientists describe how hornets are killed within 10 minutes when they are trapped inside a ball of bees.

Japanese giant hornets, which can be up to 5cm long, are voracious predators that can devastate bees' nests and consume their larvae.

But, if the bees spot their attacker in time, they mount a powerful defence in the form of a bee ball. This study found that the heat inside the bee ball alone was not enough to reliably kill the hornets.