Saharan ants control electromagnetic waves to survive heat

19 Jun 2015

Saharan silver ants get their shiny, mercury-like appearance from their coat of uniquely shaped hairs

Norman Nan Shi and Nanfang Yu, Columbia Engineering

Saharan silver ants use a uniquely shaped coat of hair to control electromagnetic waves, it has been discovered, allowing them to keep cool in their scorching habitat.

An international team of entomologists and physicists, based in the US and Switzerland, studied the North African ants -- known to live in some of the hottest temperatures on Earth -- to discover their survival mechanisms.

The ants, which forage and dig their burrows in the midday Saharan sun, when temperatures reach up to 70 degrees, must keep their own body temperatures below 53.6 degrees: their critical thermal limit.

The researchers found that the insects are covered in a triangular-shaped cross-section of hair on their backs and sides, which can manipulate electromagnetic waves right across the spectrum. This silvery coat, which means the ants often resemble drops of mercury running across the Saharan floor, allows them to cool their bodies down in two ways.

The hairs increase the reflectivity of the ants' body surface on the solar spectrum (in the visible and near-infrared range). They also enhance the ants' ability to emit excess heat via thermal radiation. This cooling effect works under a fully blazing Sun, when the Saharan ants' bodies are exposed to a clear sky, and enables them to reduce their body temperature by around 5 to 10 degrees, compared to if they didn't have the coat.

The hairs grow parallel to the skin and have triangular cross-sections

Norman Nan Shi and Nanfang Yu, Columbia Engineering

"This is a telling example of how evolution has triggered the adaptation of physical attributes to accomplish a physiological task and ensure survival, in this case to prevent Sahara silver ants from getting overheated," said Nanfang Yu, an assistant professor of applied physics at Columbia University School of Engineering.

It's hoped that the findings could lead to biologically inspired cooling surfaces that could be applied to everything from cars and buildings to clothing.

Yu and his team next plan to broaden their research to other animals living in extreme conditions, in order to better understand their survival strategies. He said: "Understanding and harnessing natural design concepts deepens our knowledge of complex biological systems and inspires ideas for creating novel technologies".