Un-crushable Beetle Surprises Scientists

A beetle that lives under tree bark can withstand crushing forces 39,000 times its body weight.

It’s called the “diabolical ironclad beetle” and scientists are intrigued. Live Science tells about its lifestyle.

Ironclad beetles (Phloeodes diabolicus) measure about 0.6 to 1 inch (15 to 25 millimeters) in length, and are found in woodland habitats in western North America, where they live under tree bark….

Diabolical ironclad beetles are almost unbreakable — you can smack them, stomp on them or run them over with a car, and they’ll scamper away uncrushed. Now, scientists know why these beetles’ outer wing cases, known as elytra, are so tough — they’re made up of a series of smoothly interlocking puzzle parts; the geometry and internal structure of this “jigsaw” design increase the strength of the beetle’s armor.

The journal Nature had this to say about research published in the issue:

The splendidly named diabolical ironclad beetle (Phloeodes diabolicus, Fig. 1) has an impressively tough exoskeleton — allowing it to survive attacks from predators, being stomped on by hikers and even being run over by cars. Writing in Nature, Rivera et al.¹ reveal the secret of this beetle’s crush resistance. Using a combination of advanced microscopy, mechanical testing and computer simulations, the authors find that layered, jigsaw-like joints and a variety of support structures connect the various parts of the exoskeleton, accounting for its toughness.

Diabological Ironclad Beetle (J. Maughn, Flickr Creative Commons License)

One of Rivera’s colleagues works at Purdue University. Their press office included a video clip showing attempts to crush the creature, then explaining the properties of its exoskeleton that confer such resistance to fracture.

In flying beetles, the elytra protect wings and facilitate flight. But the diabolical ironclad beetle doesn’t have wings. Instead, the elytra and connective suture help to distribute an applied force more evenly throughout its body.

“The suture kind of acts like a jigsaw puzzle. It connects various exoskeletal blades – puzzle pieces – in the abdomen under the elytra,” said Pablo Zavattieri, Purdue’s Jerry M. and Lynda T. Engelhardt Professor of Civil Engineering.

The video shows how the sutures interlock and absorb energy. But did this beetle evolve from a flying beetle? The scientists are only assuming so. Other insects, like ants, have flying and non-flying forms that exist side by side.

As usual, the study of organisms often leads to practical applications. New Scientist says, “Near-uncrushable beetle’s exoskeleton could inspire tough structures.”

Kisailus hopes that understanding the diabolical ironclad beetle’s uniquely tough structure will help inform the design of stronger components for use in building lighter aircraft, resulting in planes that consume less fuel and emit less carbon dioxide. “No need to reinvent the wheel, just figure out what nature’s done,” he says.

As a test, he and his team joined together a carbon-based material with a piece of metal, mimicking the joint structure of the beetle’s exoskeleton. They found it was about twice as tough as a standard joint commonly used to connect similar parts when building aircraft.

As for the beetle’s origin, writer Layal Liverpool confesses, “Why this species of beetle evolved such a tough exoskeleton in the first place is a mystery.”

Make Like a Beetle

In August, New Scientist reported on a beetle-bot created by biomimetics engineers at the University of Southern California. Named RoBeetle, it carries 2.6 times its own weight and is powered by methanol. Next they would like to make it fly. Upgrading it to a model that could lay eggs and reproduce itself is a long, long way off.

Record holder

Speaking of flying beetles, a team of scientists from Lomonosov Moscow State University found some exceptional ones. Publishing in PNAS, they reported on “Extraordinary flight performance of the smallest beetles” — specifically, tiny ones called featherwing beetles. Despite their small size, they outperform larger bugs, thereby violating a rule of aerodynamics:

We report a comparative study of speeds and accelerations in the smallest free-living insects, featherwing beetles (Coleoptera: Ptiliidae), and in larger representatives of related groups of Staphylinoidea. Our results show that the average and maximum flight speeds of larger ptiliids are extraordinarily high and comparable to those of staphylinids that have bodies 3 times as long. This is one of the few known exceptions to the “Great Flight Diagram,” according to which the flight speed of smaller organisms is generally lower than that of larger ones. The horizontal acceleration values recorded in Ptiliidae are almost twice as high as even in Silphidae, which are more than an order of magnitude larger.

Records are made to be broken, even in the world of insects.

Creatures are often over-engineered for their needs. It is doubtful that these ironclad beetles need constant protection from cars and rolling boulders. If evolution had made them this well-designed for crush resistance, every member of the species would have gone extinct long before the Stuff Happens Law hit upon enough chance mutations to produce a beetle with sutures just right to resist the immense crushing pressures measured by the scientists that this creature is able to survive. And if by some miracle one happened along, what if it couldn’t find a mate? This beetle is so well designed, it looks angelic, not diabolical.

Over-design is a hallmark of excellence far beyond minimum requirements. No wonder God’s creations inspire imitation by the top scientists in the world, who with their best efforts, cannot come close to imitating all the systems contained in this humble black beetle: movement, digestion, navigation, sexual reproduction, instincts, senses, and superior armor.