Wednesday, April 21, 2010

Zombie cockroaches

If you can bear to read about wasps and roaches, this is pretty interesting:
... let me just refresh your memory about what the Emerald Cockroach Wasp actually does.

* * * The Emerald Cockroach Wasp needs a live, tame cockroach to feed its babies.

When the female wasp is ready to lay her eggs, she seeks out a cockroach. Landing on the prospective host, she delivers two precise stings.

The first she delivers to the roach’s mid-section, causing its front legs to buckle. The brief paralysis caused by the first sting gives the wasp the luxury of time to deliver a more precise sting to the head. The wasp slips her stinger through the roach’s exoskeleton and directly into its brain.

She injects another venom that robs the cockroach of the ability to start walking on its own. The wasp takes hold of one of the roach’s antennae and leads it, like a dog on a leash, to its doom: the wasp’s burrow. The roach creeps obediently inside and sits there quietly as the wasp lays her egg on its underside. The wasp leaves the burrow, sealing the opening behind her.

The egg hatches, and the larva chews a hole in the side of the roach. In it goes. The larva grows inside the roach, devouring the organs of its host, for about eight days. It is then ready to form a pupa inside the roach. After four more weeks, the wasp grows to an adult. It breaks out of its pupa, and out of the roach as well. Only then does the zombie cockroach die.

The zombifying sting has long fascinated scientists. It does not paralyze the roach. It does not put it to sleep. If the zombie roach is frightened, it jumps in the air like a normal roach, but then it fails to run away. What does the wasp understand about the nervous system that we do not?
Answer at the link, plus lovely cockroach photos. Via 3QD.

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