Friday, February 13, 2009

Killer Viking Ninja Hornets

Who said science is boring? While reading the following excerpts from this book review visions of Viking raiders with ninja swords lopping off the heads of defenseless villagers swirled through my head. The book is entitled "Why evolution is True" by Jerry Coyne.

Coyne’s chapter on “The Engine of Evolution” begins with a splendidly macabre example. Giant Japanese hornets raid the nests of honeybees to feed their larvae. A single hornet scout discovers a beehive and marks it “for doom” with a sort of chemical black spot.

"Alerted by the mark, the scout’s nestmates descend on the spot, a group of twenty or thirty hornets arrayed against a colony of up to 30,000 honeybees. But it’s no contest. Wading into the hive with jaws slashing, the hornets decapitate the bees one by one. With each hornet making heads roll at a rate of forty per minute, the battle is over in a few hours: every bee is dead, and body parts litter the hive. Then the hornets stock their larder."

Coyne’s purpose in telling the story is to contrast the terrible fate of European bees, introduced into Japan, with native Japanese bees that have had time to evolve a defence.

"And their defense is stunning – another marvel of adaptive behavior. When the hornet scout first arrives at the hive, the honeybees near the entrance rush into the hive, calling nestmates to arms while luring the hornet inside. In the meantime, hundreds of worker bees assemble inside the entrance. Once the hornet is inside, it is mobbed and covered by a tight ball of bees. Vibrating their abdomens, the bees quickly raise the temperature inside the ball to about 117 degrees Fahrenheit. In twenty minutes the hornet scout is cooked to death, and – usually – the nest is saved."

Coyne adds that the bees can survive the high temperature, but it is another insight of the “gene’s eye view” that this would not be necessary in order for natural selection to favour the adaptation. Worker bees are sterile: their genes survive, not in the workers themselves but as copies in the bodies of the minority of hive members destined for reproduction. If the workers in the centre of the ball were cooked alongside the hornet, it would be well worth the sacrifice. Copies of their genes “for cooking” live on.

I wonder if there is room in Valhalla for boiled Japanese hornets.

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