Cockroaches, Karate and Eluding a Zombie Death

Nothing sends people scrambling for a boot faster than the sight of a scurrying cockroach. But to the pests, there are far scarier dangers out there.

True terror? That’s getting zombified — and then eaten alive.

When some unlucky American cockroaches encounter the emerald jewel wasp, the wasp delivers a paralyzing sting to the roach’s body. Then, with surgeon-like precision, it injects a mind-altering cocktail into the roach’s brain. The roach, now a zombie slave, is forced to cater to the wasp’s every whim. But the wasp has only one desire: to reproduce.

Like a handler leading a horse, the wasp grabs hold of the roach’s antenna and steers it into a hole. There, it lays an egg on the roach that eventually hatches into a hungry larva that chows down on the cockroach. When the baby matures, it bursts from the roach’s chest ready to continue the gruesome ritual.

“It’s kind of straight out of Alien,” said Kenneth Catania, a biologist from Vanderbilt University in Tennessee, “and it’s about the only thing I can think of that’ll make you feel sorry for a cockroach.”

But as Catania has studied, some roaches defend themselves from the wasps with a swift and powerful karate kick.

Using high-speed cameras, Catania recorded scuffles between adult roaches and wasps in his lab and documented the cockroaches’ defensive techniques in a paper published last month in the journal Brain, Behavior and Evolution.

First, some roaches detected an intruding wasp with their antenna. Next, they raised themselves up, as if on stilts, and lifted their hind legs. And then they waited until just the right moment when the wasp tried to strike. In that instant, the roaches knocked back the would-be attacker with brutal kicks.

“It reminded me in slow motion of one of those old Batman and Robin videos where you see the words ‘Pow’ appear on the screen,” said Catania.

Roaches’ legs are covered in spikes that act like barbed wire, making the hit extra damaging.

Although the strike doesn’t kill the wasp, it makes the attacker back off. Catania found that 63 percent of the cockroaches that defended themselves were able to avoid getting stung by the wasp. But the roaches that didn’t put up a fight nearly always got stung.

Scientists don’t know why not every roach fights back, and Catania would like to study whether the kick evolved specifically to combat the wasp or as a general method of self-defense.

Whatever the answer, it seems that striking the first blow keeps the American cockroach from becoming a mindless zombie.