Neither the Hercules Beetle Nor the Horned Dung Beetle,This is the World's Toughest Beetle - Animalassic

On the western coasts of North America, there lives a beetle that grows no longer than 3 cm in length and weighs no more than 0.5 grams but can withstand a force 39000 times its body weight, survive being run over by a car and have one of the most crush-resistant exoskeletons known to exist. This super-tough beetle is known as the Diabolical ironclad beetle (Phloeodes diabolical).

Diabolical ironclad beetle (Phloeodes diabolical)

Diabolical Ironclad beetle by David Kisailus  

The beetles belong to family Zopheridae and primarily feed on fungi and decaying plant matter.They not only have a cool name, but also have one of the strongest exoskeletons of any known insect.

Ironclad beetles have given up flight and have instead developed rather crush-resistant exoskeletal forewings — called elytra — as a form of protection to deal with predators. They have a very long lifespan for a beetle, around 7-8 years.

Diabolical iron clads are known for their toughness. Their thick, densely layered, and interlocking elytra (modified, hardened forewing of beetles) can support a maximum force of 149 newtons at a body weight of half a gram, which is equivalent to a 200-pound man enduring the weight of 7.8 million pounds! 

To test the beetle's durability, In 2015, Dr.Jesus Rivera placed an ironclad beetle on the asphalt of a parking lot and had a colleague run it over with a Toyota Camry. Twice.

Even after being bashed beneath the wheels of a 3,500-pound sedan, he discovered that the inch-long insect made it through unscratched.

Utilizing a jigsaw-like layering of their joints and appendages provides stability to withstand such extreme forces. This is done by layering multiple different scales of different sizes, ranging from microscopic to visible sizes, providing exceptional mechanical strength. The jigsaw pattern seen is a multilayered exoskeleton, including a waterproof epicuticle, an underlying exocuticle, and lastly an internal endocuticle.

In each of the cuticles, polysaccharide α-chitin combine with proteins to form fibers within each layer. These fibers are twisted and stacked upon each other creating a "helicoid" arrangement, forming laminated structures. This formation allows for sturdy, energy-absorbent, and tolerant structures. The skeleton's ability to absorb energy allows it to deflect, twist and arrest crack propagation between layers.

Slice of a diabolical ironclad beetle’s shell by David Kisailus

Two main areas allow the skeleton to withstand forces up to 39,000 times its own body weight. The first is the connection between the two halves of the shell: the interconnections are zipper-like and stiff, resisting bending pressure. The beetle's back is not interlocked in the same way, allowing the bottom halves to slide past each other and absorb squishing compression. The second area is the puzzle-like design that runs the length of the back connecting the left and right sides.

Protrusions known as blades fit together like jigsaw puzzle pieces, held together by proteins that aid in damage resistance.

The protection allows the beetle to be almost predator-proof. 

Their shell provides many issues for entomologists trying to display their specimens. The beetles cannot be mounted ordinarily with stainless steel pins; instead, they had to drill holes in the shell where the pin is to be placed.

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References

 
• Nature magazine, Davide Castelvecchi. “This Beetle’s Stab-Proof Exoskeleton Makes It Almost Indestructible.” Scientific American, 23 Oct. 2020, www.scientificamerican.com/article/this-beetles-stab-proof-exoskeleton-makes-it-almost-indestructible.
 
• Chen, Po-Yu. “Diabolical Ironclad Beetles Inspire Tougher Joints for Engineering Applications.” Diabolical Ironclad Beetles Inspire Tougher Joints for Engineering Applications, 21 Oct. 2020, www.nature.com/articles/d41586-020-02840-1.
 
• ELIZABETH PENNISI. “Even a Car Can’t Kill This Beetle. Here’s Why.” AAAS, 21 Oct. 2020, www.science.org/content/article/even-car-can-t-kill-beetle-here-s-why.