Invertebrates
Jewel Wasp
Ampulex compressa · also called jewel wasp, emerald cockroach wasp
The jewel wasp performs one of the most precise acts of manipulation in nature. With two carefully aimed stings — one to the thorax, one directly into the cockroach’s brain — it removes a roach’s will to flee, then walks the still-mobile victim into a burrow by the stump of its antenna and seals it in as living food for a single larva.
Overview
Jewel wasps live in warm regions of Asia and Africa, and have been introduced elsewhere. About 2 cm long with a metallic blue-green sheen, adults feed on nectar, but each female hunts a cockroach to provision one offspring.
Two stings, one zombie
The first sting briefly paralyses the roach’s front legs; the second, into precise regions of the brain, removes its drive to escape without paralysing it.
Walked to its tomb
The wasp bites off part of an antenna and uses the stub as a leash, steering the docile roach into a burrow, where it lays one egg and seals it in.
Status
The jewel wasp is Not Evaluated but common, and has been introduced to some islands as a cockroach-control experiment.
Jewel Wasp: common questions
How does the jewel wasp turn a cockroach into a zombie?
The female wasp delivers two separate, remarkably precise stings. The first goes into the cockroach's thorax and briefly paralyses its front legs, immobilising the roach just long enough for the wasp to line up the second, critical sting. That second sting is injected directly into the cockroach's head and targets specific clusters of nerve cells in the brain that are involved in initiating and maintaining the drive to walk and escape. The venom does not paralyse the cockroach or shut down its body, but it suppresses that escape motivation for an extended period, leaving a roach that can still move normally when prompted but has lost the impulse to run away or defend itself.
Why does the jewel wasp lead the cockroach instead of carrying it?
A cockroach is far too heavy for the small wasp to carry or drag any distance, so instead of transporting a fully paralysed victim the way many parasitic wasps do, the jewel wasp exploits the fact that its venom leaves the roach able to walk. After the brain sting, the wasp bites off roughly half of one of the cockroach's antennae, feeds on the fluid that leaks out, then takes hold of the remaining antenna stub and uses it like a leash, steering the docile cockroach on its own six legs into a burrow the wasp has prepared. This lets the wasp move a meal many times its own weight with almost no effort.
What happens to the cockroach after it is sealed in the burrow?
Once the subdued cockroach is inside the burrow, the wasp lays a single egg, glued to the underside of the roach, and then seals the burrow entrance with pebbles and debris, leaving the roach entombed alive. The wasp egg hatches after a few days, and the larva chews a hole in the cockroach's side and begins feeding, first on fluids from the outside, then burrowing into the body cavity. It eats the internal organs in a particular sequence that keeps the cockroach alive and its tissues fresh for as long as possible, only killing it near the end, after which the larva spins a cocoon inside the emptied body and later emerges as an adult wasp.
Is the jewel wasp dangerous to humans?
No. The jewel wasp's elaborate sting sequence is precisely adapted for manipulating a cockroach's nervous system and is of no consequence to a human, and the wasp is not aggressive toward people or large animals. A jewel wasp can sting if handled roughly, and the sting would feel like a minor prick, but it has no significant venom effect on humans and the wasp has no interest in defending itself against anything as large as a person. Its entire specialised behaviour is directed at a single purpose, providing a living host for its offspring.