Researchers discover secrets of the nearly indestructible ironclad beetle

There is a type of beetle known as the ironclad beetle in Southern California that is incredibly tough and hard to kill. The ironclad beetle is so strong it can survive being run over by a car. Material scientists from UCI have discovered the design secrets of the nearly indestructible insect.

The incredible survival capability of the insect is the result of two key factors. Those factors are its ability to play dead convincingly and an exoskeleton that's one of the toughest and most crush-resistant structures known to exist in the biological world. Researchers from the University of California, Irvine, and other institutions have revealed the material components and their nano and micro-scale blueprints that make the insect so indestructible.

The team has also demonstrated how engineers can benefit from these designs. The beetle can be found in the southwest portion of the United States under rocks and in trees squeezed between the bark and the trunk. The beetle can withstand a force of about 39,000 times its body weight.

For a 200-pound human to match that feat, it would have to survive a weight of 7.8 million pounds. Using high-resolution microscopic and spectroscopic evaluations, researchers learned that the secret to its survivability is in its exoskeleton's material makeup and architecture, specifically its elytra. In beetle types that fly, elytra are the forewing blades that open and close to protect the flight wings. In the ironclad beetle, elytra evolved to become a solid protective shield.

Scientists found the elytra consists of layers of chitin and a protein matrix. Compared to a flying beetle, the ironclad beetle has outer layers with a significantly higher protein concentration at about 10 percent more per weight. The geometry of the medial suture joining the two parts of the elytra together also looks like interlocking pieces of a jigsaw puzzle. Tests confirm that during compression, the suture slowly delaminates without catastrophic failure during the compression process.