In his Warwick Prize-winning book Dazzled and Deceived: Mimicry and Camouflage Peter Forbes tells the fascinating story of mimicry and camouflage in science, art, warfare and the natural world. Here the author discusses concepts of mimicry and camouflage, illustrating how they apply in nature, from tropical butterflies in South America, to peppered moths in industrial Manchester.
Article by Peter Forbes
Dazzled and Deceived is a quest book: the search for the mystery of form in nature, in particular those forms and patterns that copy the patterns of other creatures and features of the environment: mimicry and camouflage. It begins in the 1850s in the Amazonian rain forest with the young English explorers Henry Walter Bates and Alfred Russel Wallace, who discovered remarkable mimicry in tropical butterflies, the Heliconidae.
One reason for writing the book was that modern genomics has been homing in on the mechanism behind such feats of evolution. With Darwin’s recognition that mimicry was one of the crucial pieces of evidence for natural selection in mind and Bates’s prophetic words “the study of butterflies – creatures selected as the types of airiness and frivolity – instead of being despised, will some day be valued as one of the most important branches of Biological science” ringing in my ears I set out to follow the research groups on the trail of the mimetic wing patterns.
This work is ongoing and will be for a long time to come but the results so far are even more startling than anyone could have anticipated. Two of the great stories relate to the peppered moth (camouflage) and Heliconius butterflies (mimicry). Most naturalists and biologist have been at pains to point out rather severely that mimicry and camouflage must not be confused: in camouflage a creature has a pattern that disrupts its outline and allows it to blend in with its background; in mimicry one creature copies the appearance of another.
The peppered moth is the classic textbook story of evolution in action. The original peppered moth lives up to its name: a subtly patterned white and greyish-black speckled moth that is well camouflaged against tree bark and lichens. In the late 19th century a much darker, almost black form emerged near industrial Manchester and soon came to dominate the North and Midlands of England, thanks to industrial pollution and sooty black tree bark. When, from the 1960s, clean air legislation and declining industry kicked in, the black peppered moth declined as fast as it had arisen.
Heliconius butterflies are a different story. They feed on passion flowers in South American forest glades. From the plants they acquire a toxin and they advertise this by means of spectacularly beautiful red, yellow, blue, orange, black and white patterns. They also band together in mimicry rings: several species wearing the same dress to send out a stronger message: DON’T EVEN THINK ABOUT IT – WE’RE TOXIC. One Heliconius, H. numata can imitate no less than 7 different species in separate mimicry rings.
What is now emerging is that the genetics of these patterns defies all previous expectations. The peppered moth was a puzzle because many other creatures have black forms (known as melanic) and the gene for this is well known. The peppered moth, however, seemed to use a different gene altogether, which remained unknown.
In May this year researchers based in Liverpool and the Czech Republic reported the genetic locus of the black form of the peppered moth and noted that this seemed to be the very same locus that had been identified as a mimicry gene in Heliconius! So much for: “mimicry and camouflage are quite distinct processes”. Heliconius butterflies have a black background to the wings against which the gaudy colours are displayed and this seems to be the reason for this surprising parallel.
It now seems that butterflies and moths derive their patterns from genetic hotspots such as the one that links the peppered moth and Heliconius. The range of patterns produced by Heliconius suggests that the fine detail of this hotspot must be very intricate. Teasing out these details out will be the next stage of the puzzle but for now we can sit back and wonder at nature’s deep processes: how a moth and a butterfly, separated by 100 million years of evolution have used the same gene for their very different purposes.
Peter Forbes is a writer, journalist, and editor with a longstanding interest in the relationship between art and science. He is the author of The Gecko’s Foot and Dazzled and Deceived: Mimicry and Camouflage (now available in paperback from Yale University Press). He is Royal Literary Fund Writing Fellow at St George’s, University of London. In March 2011 he was awarded the £50,000 Warwick Prize for Writing for Dazzled and Deceived.