The locust had landed on the sand and instantly fried. But in the photograph three darkling beetles were happily feeding on the carcass, completely unperturbed by the extreme heat. Knowing that metallic beetles have sophisticated optical reflectors, we hoped to find reflectors for infra-red wavelengths, the heat-producing radiation from the sun. All the signs were there, but our study was interrupted by the discovery of a different structure on top of the reflector, a structure that collects water from desert fogs.

The project began with the trapping of live specimens. Collecting beetles from Namibia is no stroll in the park, so we called in the experts.
Darren Mann and Dorothy Newman from the Oxford University Natural History Museum were experienced explorers of the Namib. They joined their man in Namibia, Eugene Marais, in the north of the country and headed south to the Namib Desert via the Skeleton Coast National Park. After a few days the engine of their Land Rover filled with sand one time too many. Unblocking the filter, a regular exercise in this region, was no longer sufficient and they became stranded near the town of Sesfontein, not exactly a picture postcard neighbourhood. They spent five days with little food and water before a mechanic arrived to fix their vehicle.
Soon after making a camp at their next destination, a young bull elephant charging directly towards them, trunk in the air, ears waving! The team leapt into their Land Rover and hid for half an hour among the light traps and entomological supplies. Fortunately the elephant decided against demolishing the vehicle, but loitered with unhealthy intent. And when he chose to leave, it was for good reason. Eugene peered out of the vehicle and calmly announced that ‘the river was coming’. With a noise like thunder a vast mudslide was heading rapidly towards the campsite, giant logs in tow. The mud came to a halt just 20 feet from their tents, but Darren Mann succumbed to another danger of the mud – disease – and become seriously ill after ingesting some of it whilst digging out the Land Rover.

Arriving in the Namib the conditions changed. The scene there was one of sweeping sand dunes. And it was hot, really hot. Walking on the sand was not an option, as the local lizards testify - they stand on only two feet at any one time, interchanging continuously. Then there was the wind. It is so strong it creates sandstorms, but does bring with it water a few times each month. Since nothing is accommodating in this region, the water does not simply flow into the Namib. It arrives as a very fine mist blown by the gale-like wind. Fortunately, the field team managed to capture the beetles we were after, although how they survived in the heat and collected water from such an adverse source remained a mystery at this stage.

After leaving the Namib, the field team managed to dodge gunfire in the north of Namibia and escape to England, where the beetles were handed over. The field trip was, at least from my point of view, a success!
The beetles arrived on my desk in a large cardboard tube. Innocently I opened the lid and immediately around 20 darkling beetles made a run for it, darting around my office at great speed. But this was good news (after they were recaptured) because it signalled that they had arrived in good health.

The black beetles had almost spherical bodies, around 2cm in diameter, suspended on thin, stilt-like legs. They survived quite happily in the artificial sand dunes built for them in the Oxford Zoology labs. They also had smaller enclosures, built upon heating devices, and containing Namib sand. We used these enclosures to test the beetles' resilience to heat. Security at the labs had to be stepped up when Dr Lawrence brought in specialised infrared cameras to create thermal images of the beetles. The ultra-expensive cameras were usually focussed on battleships off Portsmouth. Now they were employed at the other end of their magnification limits.

We soon discovered that the beetle’s exoskeleton, in addition to the well-known heat-shock chemicals inside the body, was extremely well adapted to heat. This study became more involved than at first expected, and is ongoing (the future looks very bright at this stage).

When we looked at the beetle cuticle in an electron microscope we made a suprising find. Not only were there unusual structures inside the exoskeleton, but unexpected structures on the outside of the beetle also. Our experiences of reflectors and water-repellent surfaces in nature told us that the external structures on Stenocara were not part of an adaptation to heat. But maybe they could explain how this beetle drinks from desert fogs.
The structures in question were small, rounded nodules, just 10 microns in size and arranged in a close-packed hexagonal pattern. The whole of the beetle’s back was covered in large bumps, and looked like a mountain range in the electron microscope. The nodules covered the sides and valleys of the ‘mountains’, but the peaks remained bare.

We chemically tested a recently dead beetle and found that the nodules were coated in wax, but the bare regions (mountain peaks) were wax-free. A surface of nodules coated with wax has strong water-repellent properties, like Teflon, while smooth, wax-free surfaces actually attract water. It was the combination of both surface types that gave the beetle the ability to drink in the Namib.
We made a simple model of the surface of Stenocara by coating a glass microscope slide in wax. Then we partially embedded tiny glass beads, about the size of the beetle bumps or mountains into the wax. The raised beads were water-attracting while the wax between was water-repelling. We lined up alternative models next to the Stenocara slide before tilting them all and spraying them with a fine mist. The Stenocara model collected by far the most water. When the mist hit a slide with a wax surface, the droplets remained minute and were simply blown away in all directions. Landing on glass, the minute droplets formed a single, flat covering of water, which evaporated under heat or streamed off the slide in an unpredictable direction. But large drops formed instantaneously on the Stenocara model, and then rolled neatly and directly to the collector at the base of the slide.

The Stenocara beetle has evolved a droplet-growing system. It tilts its body into the fog-laden wind and minute water droplets are repelled from the mountain sides and troughs towards the peaks, where they soon become large drops. At around 5mm in diameter they roll down the beetle’s back towards its mouth, guided by the slight purchase afforded by other peaks along its path. By this stage the drop is large enough to roll into a strong wind, and is not blown off the beetle. Five millimetre drops are formed on the beetle in a steady, self-replenishing stream.
Our project had revealed some interesting biology, but more enticing was that we had made a simple model of the beetles' surface that could efficiently collect water from rapid mists. We had made, via some controlled stumbling, a beneficial device.

Much of the globe exists, like the Namib, under desert conditions with intermittent wind-blown fogs. In fact the experimental renewable technology of fog harvesting is being used in 22 countries on six continents. A square metre of netting vertically suspended in the path of wind-blown fog, such as the camanchacas of Peru and Chile, can collect 5-13 litres of water for drinking and irrigation each day.

The Defence Evaluation Research Agency (now QinetiQ) at Farnborough made up the Stenocara surface on a large scale, easily reproducing it in sheet form via injection moulding or printing techniques. The prototypes collected several times more water than can be collected by netting and was also more resilient. We applied for a patent* and large-scale manufacture is planned. The long-term goal is to employ the fog-collecting device on tents and on the roofs of buildings. But the first-stage is to produce stacks of tilted sheets containing the Stenocara surface. Hopefully these will greatly aid farming in inhospitable regions of the world.

We are also looking at other applications for the beetle surface, including devices to remove traffic-stopping fogs at airports, and to collect vapours within condensers in a controlled manner.

Beetles have once again proved to be the ultimate terrestrial animals. Not only can they survive in Canadian ice caves below -80°C, and on sand hot enough to fry a locust, but they can also drink where water appears not to exist! Oh, and they have almost everything covered in between. This particular story is a nice case of biomimetics – the extraction of good design from nature. And the word from within this recently rejuvenated subject is that further successes are on their way, some involving beetles once more.