Nature’s unspeakable cruelty (2)

My previous article dealt with the pure cruelty that animals often display— the unbearable, pitiless suffering they can inflict on fellow creatures. Today the latest edition of Scientific American reminded me of another case of unadulterated cruelty in the animal world. As a young boy my father showed me it happening, although at the time I did not catch all the details. The Siam article supplied these, and it is a story I am going to retell. In the end you will feel sympathy and compassion for — want to guess? — the common cockroach! The one we swat with impunity.

Let me start with the following scenario: a very tough space traveller, a military man in heavy armour, encounters an alien enemy. The adversary is much smaller and weaker, but has profound medical expertise. He injects a neurotoxic agent, carefully probing with the needle for a very specific area of the brain of the space traveller. The neurotoxin pacifies the victim and renders him unable to defend himself, to fight the alien off.

After that the attacker is free to start probing for a different region of the brain, in which he proceeds to inject a carefully compounded dopamine-like toxin (γ-aminobutyric acid). This causes the space explorer not to engage in any defensive actions. The toxin does not affect his motor abilities, he just has no will to flee or take evasive action. It is a classical case of chemical mind control.

Now the attacker leads him to a dark room. The victim is unable to resist, and follows obediently. The alien carefully looks for a fleshy location on his leg and attaches a capsule there. He seals the room. After a few days an alien embryo hatches from the capsule and burrows into the body of the space traveller. There it feeds on his flesh and organs, developing into an adult organism, which then breaks out of the host (like on the Nostromo in Alien) and goes on to attack the other space travellers.

Are you suitably horrified? Clearly this is just a loathsome invented scenario, one that could never occur in real life. You would think. But it does, in the insect world, where it is perpetrated by this incredibly beautiful creature:

The emerald cockroach wasp or jewel wasp (Ampulex compressa)

Essentially what the female jewel wasp does is to hunt down a cockroach, which is much larger than itself. It stings it, injecting a carefully compounded neurotoxin into a thoracic ganglion to partially paralyse it. Then the wasp probes with its stinger for the location for its second sting, which is delivered at the precise spot in the cockroach brain which controls its escape reflexes.

The jewel wasp zombifying a cockroach, with surgical precision.

The wasp is too small to carry its victim, which is why it has left the roach passive but mobile. It leads it to a burrow, guiding it by pulling on one of the roach’s antennae, which it has carefully shortened to a convenient length. In the burrow, the wasp lays an egg, at a precise location between the roach’s legs. It then seals the burrow entrance.

The zombified cockroach rests in the burrow, and after three days the wasp’s egg hatches. The larva chews its way into the abdomen of the roach and proceeds to live as an endoparasite, consuming internal organs. After eight days it enters the pupal stage, and eventually a fully grown wasp emerges from the cockroach body to begin its adult life. It goes on to seek a mate, get impregnated and parasitize new roaches.

You can watch the entire process, vividly filmed and narrated by Dave Gillies, in this Team Candiru video (warning: some readers may find it disturbing):

Paralysing a victim and making it live food for offspring also occurs in other species, but none with such surgical precision as displayed by the jewel wasp.

Feeling sorry for the poor cockroach?



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The Friedel Chronicles

The Friedel Chronicles


Frederic Alois Friedel, born in 1945, science journalist, co-founder of ChessBase, studied Philosophy and Linguistics at the University of Hamburg and Oxford.