from the almost-as-good-as-'them' dept.
Reservoir Hill writes "Zombie insects might sound like a B-movie plot device (quicktime video) but to the emerald cockroach wasp (Ampulex compressa), they're a tried and tested way to provide food for their hungry larvae. The wasp relies on cockroaches for its grisly life cycle but unlike many venomous predators, which paralyze their victims before eating them, the wasp's sting leaves the cockroach able to walk, but unable to initiate its own movement. Researchers have discovered that the wasps sting the cockroaches once to subdue them, then administer another, more precise sting right into their victim's brain. The venom works to block a neurotransmitter called octopamine with a similar action to dopamine, which is involved in preparations to execute complex behaviors such as walking. Then the wasp grabs the cockroach's antenna and leads it back to the nest 'like a dog on a leash', says one researcher. The team found that they could restore spontaneous walking behavior in stung cockroaches by giving them a compound that reactivates octopamine receptors in the insects' central nervous system. Researchers were also able to create their own zombies by injecting unstung cockroaches with a compound that blocks the receptors producing a similar effect to that of the venom."