Dazzled and Deceived: mimicry and camouflage, By Peter Forbes

Soldiers used to be conspicuous, then they turned cryptic. Cockades and braid yielded first to greys and drab, then to subtle patterns that wrapped troops in forest or desert cloaks. In nature, the same alternatives are available. Typically, it is the males of a species that opt to be conspicuous and the females that prefer to be cryptic, the males standing to gain more, in reproductive terms, from showing off. They advertise their presence and boast of their fitness to potential mates, as Darwin recognised.

His insight was based on the power of female choice, a notion that in his day ran even more strongly counter to conventional wisdom than that of natural selection itself. Evolutionists who thought of adaptations as aids to survival, rather than reproduction, doubted that nature would favour traits that drew a creature to the attention of its foes.

Abbott Handerson Thayer, an American artist, contended that even the most extravagant natural displays were in fact camouflage. To make his case he painted a peacock embedded in a mosaic of treetop foliage, its blue neck blending in with a patch of sky, and flamingos feeding at sunset. With favourable weather conditions, a flamingo's camouflage would be right twice a day, like a stopped clock.

Thayer's scrutiny of natural patterns did produce insights which later found application in the art of war. He recognised the power of patterning to disrupt the outline of an object, a principle now affirmed in military uniforms around the world. In the First World War, disruptive colour schemes were applied to ships. Whether they interfered with the enemy's aim was doubtful, but "dazzle" patterns proved good for crew morale. Sailors appreciated being aboard works of modern art.

In the Second World War, disruptive patterning was reintroduced to the Royal Navy through the initiative of Peter Scott, later one of Britain's best-known naturalists, who had read Thayer and designed a camouflage scheme for the destroyer on which he was serving. This traffic in ideas, from biology through art to warfare, provides Peter Forbes's Dazzled and Deceived with an intriguing and fluent narrative. It reaches its battlefield climax with the desert battle of El Alamein, where Montgomery's forces orchestrated thousands of dummy and disguised vehicles.

At El Alamein tanks were disguised as lorries; in nature weaponless species disguise themselves as dangerous ones. The Victorian naturalist Henry Walter Bates described how harmless butterflies in the Amazon mimicked noxious ones, "a most beautiful proof" of the theory of natural selection.

As Forbes remarks, butterflies and moths are particularly suited to demonstrating the action of evolution because as insects their generations turn over quickly, allowing the effects of selection to appear within researchers' timescales, and because they can be read like open books: "their whole being is displayed on their wings."

Ever since Darwin, the means by which butterflies and moths mimic each other, or their surroundings, have been the focus of controversies. These include theoretical debates which began in the 1920s, about whether evolution proceeds in small steps or dramatic leaps, and recent creationist attempts to discredit the hypothesis that peppered moths grew dark because these variants were better concealed from birds in areas blackened by industrial pollution.

Forbes himself is excited by what the genetics of mimicry can reveal about the relationship between evolution and how individual organisms develop. His fascination with butterflies and moths leaves no room for, among other things, the 400 species of orchids that get themselves pollinated by tricking insects into trying to mate with them. But there is more than enough to read on butterflies' wings.

Forbes's emphasis makes this a distinctively British story, reflecting what the American geneticist Richard Lewontin called "the fascination with birds and gardens, butterflies and snails... characteristic of the pre-war upper middle class from which so many British scientists came."

Forbes takes umbrage at what he sees as "ad hominem prejudice" rather than engaging with Lewontin's implication that the British researchers' science was shaped by their backgrounds. His preference for empirical findings rather than debates about the relationship between science and its social context is itself rather British.

The story has largely run its course. Military camoufleurs may not have much left to learn about concealment from nature, which has little to tell them about how to make objects invisible to radar. Meanwhile, something curious seems to be happening to disruptive patterns.

Security forces are appearing in streets and trouble spots in increasingly vibrant shades of blue, purple or pink. They might conceivably find themselves camouflaged for a moment, like Thayer's flamingos, if they came under fire in a fashionable bar. But the real purpose must simply be to signal that these are soldiers, or as good as, and the colours are to make them stand out.

Russian fighter jets also come in fetching shades of blue, arranged to form intricate synopses of the sky. Some of these schemes have reinvented the dazzle pattern, possibly to dazzle enemy pilots, but more likely to dazzle visitors at air shows. US warplanes remain grey: the Americans don't need paint schemes to highlight that they are in a military league of their own. Lesser forces are rediscovering the attractions of conspicuous display, and following the lead of the fashion designers who first turned camouflage into style.

Marek Kohn's 'A Reason for Everything' is published by Faber & Faber