Balls of Fire: Bees Carefully Cook Invaders to Death

Article excerpt

Honeybees that defend their colonies by killing wasps with body heat come within 5[degrees]C of cooking themselves in the process, according to a study in China.

At least two species of honeybees there, the native Apis cerana and the introduced European honeybee, Apis mellifera, engulf a wasp in a living ball of defenders and heat the predator to death. A new study of heat balling has described a margin of safety for the defending bees, says Tan Ken of Yunnan Agricultural University in Kunming, China.

He and his team also report in an upcoming issue of Naturwissenschaften that the native bees have heat-balling tricks that the European bees don't. That makes sense, the researchers say, since the Asian bees have long shared their range with the attacker wasp Vespa velutina, but the European bees became widespread in Asia only some 50 years ago and so have had much less time to adapt to the wasp.

The attacker wasps are "gigantic," says Thomas Seeley of Cornell University, who studies bee behavior. Of all social insects, the species has the largest workers, with wingspans that can stretch 5 centimeters. The wasps build large versions of the papery nests of hornets found in North America, and they specialize in breaking into other social-insect nests and carrying off larvae as food for young wasps.

"I've seen a single wasp overwhelm a colony of 6,000 bees" of a species that doesn't make heat balls, says Seeley. The invader wasp stands at the nest's entrance as one guard bee after another comes out to defend its home. "The wasp cuts the guard into pieces ... and waits for the next one," says Seeley. …