Japanese Honeybees Versus Hornets

Found on Crypto-Gram for 11/15/2002.

Giant hornets regularly attack beehives. Typically, an attack begins when a single hornet captures a lone bee nearby the hive. After several of these perimeter skirmishes, one hornet leaves a marking pheromone at the hive's entrance. This pheromone attracts the other hornets, who arrive en masse and attack the beehive. The bees' stingers can't penetrate the hornets' armor, so it's a one-sided slaughter; something like 30,000 bees can be killed in a few hours by 30-40 hornets.

Japanese honeybees, however, have evolved an interesting defensive strategy. When a hornet marks the hive's entrance, the bees guarding the entrance return to the hive and wait for the attacking hornets. This has the effect of luring the first attacking hornets into the hive, rather than allowing them to start their attack outside. Simultaneously, over 1000 worker bees in the hive leave the combs and mass just inside the hive's entrance. When a hornet tries to
enter the hive, the workers surround it, forming a ball of bodies, and cook it to death with their body heat. The bees also release a pheromone that draws ever more bees from the hive's interior to come to the entrance and defend the nest.

This strategy must be perfect in order to be successful. If the bees fail in killing the first hornet attackers, then the hornet pheromone gets stronger, and more hornets arrive to reinforce their attack. By sheer numbers, the hornets can overpower the bees.

Source: Bernd Heinrich, "The Thermal Warriors: Strategies of Insect Survival," Harvard University Press, 1996.