World's strongest creature harbours colour change secret

Not only is the aptly named Hercules Beetle the strongest creature in the world, capable of lifting 850 times its own weight, it mysteriously changes colour depending on the humidity.

World's strongest beetle looks pretty formidable in green or black

Scientists have been studying the beetle’s shell in the hope it will help the design of ‘intelligent materials’ and now they think they may have cracked its secret.

Researchers from the University of Namur in Belgium used a scanning electronic microscope to study the structure of the beetle’s shell and a spectrophotometer to study the light interactions, which determine the colour. They found that light interferes with the unique shell to produce a green shade but when water enters into the porous shell it destroys the interference leading to a black colour. In the laboratory they established that while dried shell specimens changed predictably with humidity, the live beetles were not so consistent.

Marie Rassart, a researcher from the University of Namur, said: “The sort of structural behaviour displayed by the Hercules Beetle could be an important property for ‘intelligent materials’. Such materials could be put to work as humidity sensors. This could be useful for example in food processing plants to monitor the moisture level.”

Questions still remain to why the rainforest dwelling Hercules Beetle’s shell changes black in humid conditions. Some think that as the rainforest nights are more humid the colour change is for better camouflage. Others speculate that it may be so the beetles can absorb heat better during the night.
The research is published in the New Journal of Physics.
 
By Leila Sattary