Scientists reveal how diabolical ironclad beetle can bear huge weights
It can survive being run over by a car, pecked by predators and crushed underfoot. Now researchers have revealed the secrets behind the near-indestructibility of the diabolical ironclad beetle.
Found in wooded areas of the US west coast, the beetle is about 2cm in length. Like some other species of flightless beetle, its wing covers, known as elytra, are not only hardened, but fused together. The upshot is a gnarly black armour that protects it from being crushed.
Researchers have revealed just how tough this armour is, finding the diabolical ironclad can withstand far greater forces than other flightless beetles from similar habitats, surviving loads about 39,000 times its body weight. That is akin to a 90kg human withstanding the weight of about 280 doubledecker buses.
“We were impressed. Especially given that this beetle does not contain any mineral – just organic components,” said Prof David Kisailus, co-author of the study from the University of California, Irvine.
Writing in the journal Nature, Kisailus and colleagues report how they examined the structure of the beetle’s exoskeleton to understand what makes it so tough.
Among their findings, they discovered that the beetle’s fused elytra were interlocked. While other beetles have interlocking elytra, the diabolical ironclad had a greater number of interlocking sections, resembling connected jigsaw-puzzle pieces. In subsequent experiments the team found this helped distribute stress and make the join more robust.
The elytra were also found to be layered and rich in proteins – features that may boost toughness. Experiments showed that when a weight was applied where the elytra join, these layers peel apart, releasing strain while leaving the join intact.
The elytra are connected to beetle’s shell on its underside, with stronger, stiffer joins where vital organs need protection, and more flexible joins elsewhere that, the team say, act a bit like springs, absorbing energy when forces are bearing down on the insect.
Further experiments showed that the features observed in the diabolical ironclad beetle’s exoskeleton could be used to develop techniques for joining materials. It was found that incorporating such features produced stronger joins than fasteners typically used in turbine engines.
“Given that nature has been optimising and performing experiments for hundreds of millions of years, there are abundant resources to provide inspiration for next-generation materials,” said Kisailus.
Max Barclay, the curator of beetles at the Natural History Museum in London, who was not involved in the study, said that while many species of beetle could fly away from threats, the flightless diabolical ironclad beetle had to toughen up to survive.
Barclay added that while most beetles lived for only a matter of weeks, the diabolical ironclad could live for about seven or eight years. “These beetles are doing the beetle-equivalent of living for 1,000 years, so they have to protect themselves against risk in a way that shorter-lived creatures don’t,” he said.