In 1859, Charles Darwin published a theory that explained how features like camouflage evolved by providing individual animals with a reproductive advantage. This process enabled creatures to leave more offspring on average than other members of the same species. The English zoologist Edward Bagnall Poulton studied animal coloration in his 1890 book The Colours of Animals. He classified different types such as special protective resemblance where an animal looks like another object. His experiments showed that swallow-tailed moth pupae were camouflaged to match the backgrounds on which they were reared as larvae. Poulton's general protective resemblance was at that time considered to be the main method of camouflage. Frank Evers Beddard wrote in 1892 that tree-frequenting animals are often green in colour. Among vertebrates numerous species of parrots, iguanas, tree-frogs, and the green tree-snake are examples. Beddard did however briefly mention other methods including the alluring coloration of the flower mantis. He also explained the coloration of sea fish such as the mackerel. Among pelagic fish it is common to find the upper surface dark-coloured and the lower surface white. This makes the animal inconspicuous when seen either from above or below.
Biological Mechanisms And Principles
The artist Abbott Handerson Thayer formulated what is sometimes called Thayer's Law, the principle of countershading. However, he overstated the case in the 1909 book Concealing-Coloration in the Animal Kingdom. He argued that all patterns and colors whatsoever of all animals that ever preyed or are preyed on are under certain normal circumstances obliterative. Thayer used paintings such as Peacock in the Woods (1907) to reinforce his argument. Teddy Roosevelt roundly mocked these views by critics. The English zoologist Hugh Cott's 1940 book Adaptive Coloration in Animals corrected Thayer's errors. Cott built on Thayer's discoveries developing a comprehensive view of camouflage based on maximum disruptive contrast. Disruptive patterns use strongly contrasting non-repeating markings such as spots or stripes to break up the outlines of an animal. Predators like the leopard use disruptive camouflage to help them approach prey while potential prey use it to avoid detection by predators. Countershading uses graded colour to counteract the effect of self-shadowing creating an illusion of flatness. Self-shadowing makes an animal appear darker below than on top. Countershading paints in tones which are darkest on top lightest below making the countershaded animal nearly invisible against a suitable background.