The Asian giant hornet

In WEIT, I begin the chapter on natural selection with a particularly gruesome example of an adaptation: the predatory Asian giant hornet (Vespa mandarina), the world’s largest wasp and a viscious killing machine.

They are horribly fricking huge, with a two-inch body (tipped with a quarter-inch stinger that injects a potent venom) and a three-inch wingspan. Their stings kill several dozen Asians yearly. Here’s what they look like:

Fig. 1. Vespa mandarina on a brave Homo sapiens.

I won’t recount the whole story here, except to say that a small band of these wasps, incited by a single scout wasp, who finds a nest and marks it for doom by depositing a drop of pheromone that attracts its confreres, can decimate a colony of 30,000 Asian honeybees in a few hours, decapitating the hapless bees with their slashing jaws. They then raid the bee colony of honey and grubs, which they bring back to their own nests to deposit in the maws of their own voracious larval wasps. Here’s a video of a wasp raid:

But the local honeybees have evolved a marvelous counter-adaptation: they mob the first scout wasp that tries to mark the beehive with a pheromone, covering the wasp with a thick ball of bees that vibrate their abdomens, raising the temperature inside the ball so high that the hornet is cooked to death (the bees can survive that temperature). Here’s a video of the cooking process:

As one might expect, the introduced European honeybee, which hasn’t coevolved with the Asian wasp, has no counteradaptation.

A relative of the hornet, the not-quite-so-dangerous species Vespa veluntina (also a predator of honeybees) , has invaded Europe in the last few years, as reported this week in the Telegraph:

The bee-eating hornets, instantly recognisable by their yellow feet, are rapidly spreading round France and entomologists fear that they will eventually cross the Channel and arrive in Britain.

Hundreds of the insects attacked a mother on a stroll with her five-month-old baby in the Lot-et-Garonne department, southwestern France, at the weekend before turning on a neighbour who ran over to help. The baby was unharmed.

They then pursued two passers by and two Dutch tourists on bikes. The victims were treated in hospital for multiple stings, which are said to be as painful as a hot nail piercing the skin

. . .The Vespa velutina, which grow up to an inch in length, is thought to have arrived in France from the Far East in a consignment of Chinese pottery in late 2004.

So far the honeybees in Europe, like the European honeybees in Asia, have no defenses against the wasp. It will be interesting to see if, over time, they evolve a cooking behavior (or, in the case of some honeybees in Cyprus, a variant in which a mob of bees surrounds the wasp and suffocates it by preventing it from expanding and contracting its abdomen).