Winging it
Nigal Williams
Current Biology, Volume 20, Issue 13, R544-R545, 13 July 2010 | doi:10.1016/j.cub.2010.06.045
Summary: A new book highlights the range of patterns evolved as a defence mechanism by butterflies that resemble aspects of other organisms. Nigel Williams reports.
Butterflies and moths are well known for their mimicry and camouflage. But most work on mimicry amongst insects has focused on how edible species have evolved to resemble toxic species or how toxic species have converged on similar warning patterns to deter predators to their mutual advantage. But in a new book “Butterflies
An Atlas moth reveals startling snake images at the tips of its wings. (Photo: copyright Stratford upon Avon Butterfly Farm Ltd.)
Howse explains how these insects have been able to evolve designs to protect them from their principal predators, which include birds, lizards and monkeys. These insectivores, Howse argues, detect their prey by perceiving small details of shape and colour rather than the whole picture of the insect. Most people have overlooked such emblematic features. But artists have picked up on the images.
“If we look at the detail of a living butterfly in the way that a bird sees it from many different angles and perspectives, surprising images reveal themselves. There are features of owl eyes, snake heads, caterpillars, lizards, wasps, scorpions, birds' beaks and feathers to be found there,” he says. “Many butterflies and moths have bizarre combinations of images on their wings and bodies which prompt comparison with the works of art of the surrealists, such as Magritte and Dali. They have a similar effect to unsettle the way in which things are normally perceived to confuse and shock.”
Among the many species discussed, Howse describes how the Atlas moth Attacus atlas has evolved the appearance of two snake heads on its wing tips. But further, the insect increases the impression of a snake by flicking movements of the wings made by the moth when disturbed, resembling the swaying movement of a snake about to strike, writes Howse.
He highlights how the eyed hawk moth (Smerinthus ocellata), is innocuous enough when viewed from the rear, but head on, it bears a striking resemblance to a fox. “The signs and symbols that appear to be so important in the animal world, like details of eyes, snakes and birds, are archetypical symbols in ours, but for us they carry very complex meanings,” he writes. Over the millennia they have been incorporated into mythologies around the world, he says.
The overwhelming appeal of the concept of evolution through natural selection has focused the minds of generations of biologists on trends, and the similarities and differences between organisms that is grist to the mill of taxonomists. “To paraphrase T.S. Eliot, ‘Where is the imagination that has been lost in knowledge and where is the knowledge that has been lost in information?’ This book is an attempt to show that there is a language in the wings of butterflies and moths,” Howse argues.
“This does not help us to understand why we see butterflies and moths as creatures that epitomise the beauty of nature, but it underlines what Darwin called the ‘grandeur’ of evolutionary theory.”
“Many insects have evolved colourings and shapes which enable them to blend in with features of their feeding and resting places, as in camouflage, or to resemble closely other species of insect that harbour unpalatable toxins,” he says. But the book reveals how butterflies and moths have greatly developed these defensive strategies.
Howse heaps praise on early keen observers of nature. “Much fascinating but neglected information about Lepidoptera is found in the writings of Victorian naturalists, starting with Charles Darwin, Alfred Russel Wallace and Henry Walter Bates,” he says. “I have also been inspired by the original approach of certain entomologists of the twentieth century such as Fabre, Hilton and the Hon. Miriam Rothschild.” He has particular praise for Rothschild. She “stands apart amongst entomologists, and the bases of many of my ideas have come from reading her publications,” he says. “Significantly, such people were not primary experimentalists, working in laboratories, but were the keenest of observers.” With the decline of so many species, often without clear and obvious reasons and often unnoticed, the role of such observers is of growing importance.
+++++
+++++
Vote neste blog para o prêmio TOPBLOG 2010.
