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New research sheds light on how the little wasp defeats the big cockroach

Not by force, but by mind. This is the tactic used by the wasp that turns the cockroach's body into a wasp's nest - literally

In the picture: the wasp stings the cockroach's head, while its legs are paralyzed and it is unable to fight. Photographer: Ram Gal.
In the picture: the wasp stings the cockroach's head, while its legs are paralyzed and it is unable to fight. Photographer: Ram Gal.

See the comments of Ram Gal, from the Department of Life Sciences at Ben Gurion University on some of the readers' responses to this article.

The next time you have a cockroach thermos on your foot, you may, in fact, commit euthanasia, since by doing so you at least put an end to the cockroach's life in a quicker action than the expected death from a wasp, which attacks it and injects poison into its brain, which paralyzes it and finally causes it to die in severe agony.

These days, a unique study is being carried out in the laboratory of Professor Frederic Libersat from the Department of Life Sciences at Ben-Gurion University in Be'er Sheva, which allows a glimpse into the mechanism by which a wasp is able to sting a cockroach directly into its brain. His research colleague, Ram Gal, who examines the interaction between the wasp and the cockroach, found that when the wasp was given cockroaches whose brains had been surgically removed, it stung his head for over 10 minutes (instead of only one minute in normal cockroaches), and even injected a small amount of venom into his head by a lot

"This finding," says Gal, "implies that the wasp finds the cockroach's brain inside its "skull" with the help of any receptors on the stinger, which are able to distinguish between the brain and other organs inside the cockroach's head. Indeed, when the stinger was scanned with an electron microscope, tiny sensor-like organelles were found, similar to the taste receptors in other creatures. It is still not clear what exactly the substances are picked up by these sensors, and which enable the wasp, apparently, to "taste" the cockroach's brain and distinguish it from other tissues." The findings of this study were published on the website of the scientific journal Science (Science Now), which was published these days.

In order to understand the importance of the researchers' findings, it is appropriate to internalize the process by which the wasp captures the cockroach and ultimately leads to its brutal death: according to Gal, the parasitic wasp Ampholex compressa (A. compressa) attacks cockroaches and uses them as a source of live food for its offspring, in the way which looks like it was taken from a creepy sci-fi scene. The wasp, with a metallic bluish-green body color and dark red legs, locates a cockroach, quietly approaches it, then suddenly and suddenly grabs it in its strong jaws and stings it in the chest area. This bite causes paralysis of the cockroach's front legs, a temporary paralysis that lasts about two minutes. This period of time, in which the cockroach is unable to fight a wasp that weighs about a third of its weight, is extremely deadly for the cockroach. The temporary paralysis allows the wasp to improve its grip, whereupon it bends its abdomen and plunges the deadly sting deep into the helpless cockroach's head. This sting is actually directed directly into the cockroach's brain, for which the wasp injects a cocktail of venom, which affects the cockroach's nervous system (a neurotoxin) and causes a dramatic change in its behavior: immediately after the sting, which usually lasts about a minute, the wasp leaves the cockroach, while it begins to be active A vigorous self-cleaner.

This cleaning, which is a direct result of injecting the venom into the cockroach's nervous system, lasts about half an hour, during which time the wasp flies around the area looking for a burrow into which it can insert the stinging cockroach. After finding a suitable place, she returns to the cockroach, which is still undergoing intensive cleaning operations and is completely unaware of what is happening around it. The wasp cuts its tentacles and drinks the blood that drips from them, without any resistance from the cockroach. Apparently, the blood that the wasp drinks serves as a catalyst for egg laying. The cockroach's suffering did not end there: the poison that was injected into his brain earlier drugged the cockroach and turned it into a kind of "zombie". He enters a depression-like state, and although he is not physically paralyzed and all the muscles in his body are able to function normally (as mentioned, the initial paralysis has long since dissipated), his motivation to move or run away completely disappears. Thus, the cockroach does not resist when the tiny wasp catches and leads him, with his full consent, into the burrow that he prepared ahead of time, and which will become his permanent home until the end of his days (which is near anyway). The cockroach remains indifferent even when the wasp lays an egg on it, and it comes out of the burrow and closes the cockroach inside with the help of small stones and dry leaves that it finds around.

The cockroach shows no signs of resistance even when, three days later, a larva hatches from the egg and bores a small hole in the cockroach's body. Through the hole, the larva enters the cockroach, and begins to eat it from the inside while still alive. This feast lasts for about three days and at the end the cockroach finally dies. The hatched larva incarnates in the cockroach's stomach, and after about three weeks, a mature wasp hatches from the cocoon, leaves the dead cockroach's stomach, and flies off to find another cockroach and start the life cycle anew. The new study by the university researchers therefore sheds new light on the way the little wasp defeats the big cockroach.

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