That’s a string of creepiness there, isn’t it? Everybody knows (I hope) the way some parasitic wasps turn caterpillars into living meat lockers for their offspring. But Science News now reveals how other parasitic wasps convert healthy cockroaches into easily controlled zombie meals-on-legs:
The female wasps (Ampulex compressa) specialize in attacking the American cockroach (Periplaneta americana). If a wasp succeeds, she leads away an unprotesting roach like a dog on a leash just by tugging at a roach antenna. Then she lays an egg on the roach and buries the insect alive as living meat for a wasp larva. Though a normal roach could dig itself out, there’s no sign that the wasp-stung ones can even try.
To the roaches, the wasp “is a dedicated, goal-oriented, deft parasitoid coming for your brain,” says neurobiologist Kenneth Catania at Vanderbilt University in Nashville. He has recently created an impressive collection of slo-mo attack videos, providing the first detailed look at how some roaches fight back.
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The attacking wasp needs victims with their nervous systems still working well enough to move. Otherwise the tiny jewel wasp would never be able get a whole roach to an egg chamber. Every wasp needs living roach meat to start life, so the evolutionary forces that hone wasp attacks are extreme, Catania says. The jewel wasp has evolved an attack that subdues a roach in just two precise stings.
For the first sting, a wasp jumps and grabs the little shield over what’s basically the back of the roach’s neck. Within literally half a second, the wasp is positioned to deliver a sting that will paralyze the front legs, making them useless for defense. The wasp then bends her abdomen around, quickly feeling the way to the soft tissues of the roach throat. The stinger itself carries sensors and stabs up through the throat to deliver venom to the cockroach’s brain.
Roaches then typically start grooming themselves, possibly as a side effect of the venom. The wasp doesn’t have to do anything else. The roach “is sitting there not running away from this really terrifying creature that’s going to eventually ensure it gets eaten alive,” Catania says.
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Stills and video at the link, full text of “How Not to be a Zombie” here, in Brain, Behavior and Evolution.