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Nosoderma diabolicum: Withstands 39,000 times the weight of its own body
Photo: David Kisailus / UCI
Beetles of the species Nosoderma diabolicum can drive their predators to despair.
Birds, lizards and rodents have difficulty getting to the meat of the animals.
The beetles that live in the southwest of the USA are extremely tough: even if they are run over by a car, they will happily crawl on afterwards.
Now a research team led by David Kisailus from the University of California in Irvine has solved the mystery of the stability of the "diabolical iron-armored beetle" - the translation of the English name "diabolical ironclad beetle".
The scientists report in the journal "Nature" that the findings could lead to better materials in the aerospace industry, for example.
The resistance is based on the special architecture of the back.
"The ground beetle is built like a small armor", explains Kisailus. "It cannot fly away, so it stays where it is and endures the attack in its special armor until the robber lets go."
A person would have to withstand almost 4,000 tons
Compression tests showed that the beetle could withstand a force of 149 Newtons.
This corresponds to almost 15 kilograms that press specifically on the small body and thus 39,000 times its weight.
This does not explain how the animals survive being driven over, but it is still astonishing: if you apply the value to a person weighing 100 kilograms, they would have to withstand a weight of 3900 tons.
"That's something special," says evolutionary biologist Alexander Blanke from the University of Bonn, who was not involved in the study.
"This beetle shows the special material properties of the insect skin in an impressive way."
But what gives it its special stability?
The carapace of the beetle consists, as in many other species, of two hard-shelled wings, so-called elytra, which are tightly interlocked on the back.
However, according to the researchers' study, the material of the armor made of chitin-containing fibers contains significantly more protein than other species, which increases its resistance.
Ultimately, however, the stability is mainly due to two edge zones of the elytra: their lateral transition zones to the belly shell and in particular the seam that connects the two elytra in the middle of the back.
These elements give the armor a unique combination of strength and flexibility.
Built-in shock absorber
The lateral connections of the back armor to the abdominal plate consist of structures that interlock firmly in the front chest area.
This increases the strength and protects the organs there.
In the rear area, the armor is more likely to rest and can be moved against the belly plate.
This acts like a kind of shock absorber and makes the transition flexible.
Thanks to these properties, the beetles can apparently press themselves under rocks or between tree trunks and their bark.
On the back, however, the seam between the two elytres looks like interlocking pieces of a puzzle under the microscope.
The "teeth" have an elliptical shape, which makes them more stable.
The layers of the armor arranged one above the other deform and loosen under load, the seam remains intact.
The researchers write that these advantages can be used in the aerospace industry, for example.
Blanke sees it similarly: "In many morphological studies, a reference to technology is established that is diffuse. But here a direct transferability is conceivable, for example in the construction of rotor blades for aviation."
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jme / dpa
