A hardcore fan of horror and fantasy films will not be much terrified by zombies, although they are literary terrifying. But if someone is in thought that these creatures are only encountered via the silver screen, not in real life, then that is a huge mistake. Meet one of the most magnificent creatures of mother nature, who makes zombies, not in the form of humans but cockroaches.
The zombie-maker is none other than the Emerald Wasp or the Jewel Wasp (Ampulex compressa). This solitary parasitic wasp is a member of the family Ampulicidae, where the cockroach-hunting parasitic wasps belong. They prefer warmer climates and are dominated in regions like Africa, South Asia, Southeast Asia, and the Pacific islands. It exhibits an unusual and distinctive procedure of “zombification ” during reproduction.
Morphology
It is an eye-catching wasp of metallic blue-green with red femoral. A Female is 2-3 cm long while a male is smaller in size. Female possesses a long stinger which male lacks. Has 3 pairs of legs.
Reproductive behavior
The main goal of zombifying cockroaches is to provide protection and to facilitate a source of ” fresh” meals to the newly hatched wasp larva, as the host.
After aiming a cockroach, the female wasp ambushes it by grabbing the cockroach from its wing base and stings once to its thorax with toxic venom. The first sting is crucial in order to subdue the host (cockroach). As a result, the front legs are paralyzed temporarily. While the cockroach is weakened and less mobile, the wasp takes the opportunity to aim precisely her second sting. After insertion of her long stinger through the neck of the cockroach to its brain(ganglia), the wasp takes a couple of minutes to inject neurotoxic venom into its host. The second sting is the most important as it enables taking over the “mind-controlling” of cockroach which makes it become a senseless, fearless zombie-like slave.
Not a single act of self-defense, aggressiveness, or attempting to escape is shown by the helpless victim. It starts to groom itself while remaining calm and immobile. This bizarre behaviour is induced by dopamine, received via the second sting.
Meanwhile, the female wasp looks for a suitable nest where it can lay eggs and detain the parasitized “zombie slave”. The returned wasp breaks/chews off one of the antennae of the cockroach and takes a few sips of the fresh cockroach blood that will energize and boost her up. Then the wasp grabs the antenna and leads the cockroach towards the dark burrow like a dog on a leash. She starts to lay and attach an egg (lays a single egg at a time in the natural environment) on the cockroach’s leg inside the nest. Before leaving, the emerald wasp conceals the entrance of the nest and makes sure it is perfectly sealed.
The egg hatches after about 2 days. The newborn larva slowly settles down within the abdomen of the living cockroach and starts to eat up all the organs except the nervous system. Then the matured larva impregnates the host with its cocoon in the abdomen. The final phase of this procedure recollects the famous and shocking chest-bursting scene of the Alien franchise. Likewise, after roughly 40 days the fully-grown wasp emerges from the cockroach and flies away, leaving behind the lifeless carcass.
Neurotoxic venom
The lethargic state of cockroaches after the second sting is caused by the wasp’s neurotoxic venom. Dopamine, which is a component of this venom, obstructs the spontaneous defensive behaviour of cockroach and induces long-term hypokinesia (7 to 10 days lethargy). Also, another component is an alpha-helical peptide (Ampulexin 1), the most common peptide in the venom that unables the mobility of cockroaches and keeps it in a sluggish state.
A fun fact is that people who are willing to experience this senseless, ” zombified” mental state can pay upwards of $500 for a dose of venom which would not be healthy at all from a cockroach’s point of view.
Other birds of prey
It is the nature of parasitoid wasps to seek hosts eagerly to carry on their reproduction cycle. Some of the victims can be named spiders, caterpillars, ants, etc.
1. Agriotypus wasp
These wasps lay and attach their eggs in an aquatic host, Silo pallipes (Caddis fly larvae). The host resides in streams of South West England. The wasp can dive and remain underwater for about 15 minutes to accomplish its task.
2. Lasiochalcidia igiliensis wasp
Found in Africa and Europe. This wasp is a risk-taker that targets and ambushes antlions with deadly jaws. Inserts eggs to the host’s throat and parasitizes it.
3. Hyperparasitoids
Hyperparasitoid is a parasite that lives in another parasite (specifically among Hymenoptera like wasps and sawflies). The reproductive behaviour of Lysibia nana exhibits this relationship.
Lysibia nana never directly encounter with its host Cotesia glomerata, also a parasitoid wasp. C.glomerata attacks and parasitizes caterpillars. It tends to lay multiple eggs on a single caterpillar. Gradually, the hosts are killed by newly-emerged larvae. They develop a cluster of cocoons nearby the carcass of the host. L.nana female wasps are capable of detecting the plants that were gnawed by parasitized caterpillars. Then they lay eggs on C.glomerata larvae (cocoon) who become a host for L.nana.
Conclusion
Emerald wasp is extraordinary evidence for neurological parasitology.
Studying its unique reproductive behavior is kind of similar to watching an R-rated horror movie, as its nature is aggressive, harsh, and merciless towards the host. Nevertheless, these creatures are part of our environment that specifically contribute to regulating certain animal population sizes and balancing the environment.
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