Ironclad beetles offer a lot to learn for engineers and entomologists

While that research holds promise for designing stronger materials, Smith is particularly fascinated with why these beetles have developed such strong body armor to begin with and how they have spread around the world. He recently received an $878,000 grant from the National Science Foundation to explore those questions.

“The fact that they can generate a matrix that’s so tough either from chemical composition or from the structure themselves is exciting from an engineering perspective,” said Smith, who was not involved with the Nature study. “These are harder than things we can make.”

The exoskeleton of beetles is made up of a single layer of epithelial cells, which secrete layers of hardened cuticle. This cuticle provides defense from the outside world and makes up the part of the beetle that we see. In darkling beetles, ironclad beetles, and other tough, flightless groups, the cuticle is extremely thick and super hard. This can be especially important for large flightless beetles that lack other means of defense.

“Generally, this comes down to a defense mechanism. They can’t fly away from predators, so they have limited options on how to avoid getting eaten,” Smith said. “If you’re really small, you can hide from predators. But these beetles tend to be larger, making them susceptible to birds and mammals. Being so tough makes it difficult for these predators to eat them. It’s dealing with a lifestyle problem, dealing with evolution.”

Many hard flightless beetles have developed other interesting uses for their tough exteriors. Fog-basking beetles in the Namib desert tilt their abdomens into the air to “collect fog.” Their tough, nonporous exoskeletons contain hydrophobic and hydrophilic regions that help condense the fog into water droplets that run down the body and into the beetles’ mouths. The tok-tokkie beetles, tap their tough abdomens to make a clicking sound to attract mates.

Smith’s NSF-funded work focuses on the evolutionary history of desert darkling beetles and how these species are using next-generation genome sequencing and morphology.

“There are certainly things we take from these beetles to improve engineering and materials, but these insects are so interesting from a biological and genetic perspective,” Smith said. “There’s so much we can learn about these beetles and how they use their distinct physical attributes to survive and thrive in difficult environments. They’re fascinating creatures.”