Beetle juice

Natural History, Feb, 2002 by Kirsten L. Weir

Scarcely any rain fails in the Namib Desert, on the east coast of southern Africa, but the dense fog that blows across it from the Atlantic Ocean several mornings each month is a source of water that can be harvested--with the right equipment.

Andrew R. Parker, of the University of Oxford, and Chris R. Lawrence, of the British research and development organization known as QinetiQ, recently discovered how beetles of the genus Stenocara collect drinking water from Namib Desert fog. The beetles' backs are covered with bumps--under a microscope, they resemble a landscape of peaks and valleys. The peaks attract water, while the valleys, with a complex microscopic structure and a coating of wax, repel it.

Facing into the wind, the beetles tilt their bodies forward as moisture from fog collects on the bumps. Once a collected droplet grows heavy enough, it rolls down to the insect's mouthparts. Water droplets roll off the hydrophobic surface of lotus leaves in the same way, but the raindrops falling on leaves are much larger than fog droplets, which are so light that they travel almost horizontally in a breeze. The beetles' hydrophilic bumps are indispensable equipment for harvesting the tiny beads of fog before they waft away.

Parker and Lawrence believe that Stenocara's structure can have practical applications on a large scale in the manufacture of vapor collectors. A tent that can gather drinking water for its occupants is in the works. ("Water Capture by a Desert Beetle," Nature 414, 2001)