Even before Charles Darwin put pen to paper to write up his theory of evolution through natural selection, entomologists knew full well that the colors of insects “deceive, dazzle, alarm or annoy” their enemies (Kirby and Spence 1815–28, 2:219). It was taken as overwhelming proof of the power and beneficence of the good god, a firm plank in the edifice of natural theology (Kimler 1983). In the standard work, An Introduction to Entomology, or Elements in the Natural History of Insects, coauthored by the parson-scientist William Kirby, a prize example was the “mimicry” of the Brazilian walking stick insect (Phasma) that so closely resembled the twigs on which it spent its living days. Although no full-blown theory was offered, it was clearly noted that it had a function, because the author “has often been unable to distinguish it [the insect] from them [the twigs], and the birds probably often make the same mistake and pass it by” (Kirby and Spence 1815–28, 2:220).

The explanation of unusual coloration was muddled, however, by natural theology’s reliance on design. Resemblance to an object or background as deceptive disguise (camouflage) made sense as a providential aid to the species, but what to make of resemblance merely to another animal? The usual answer for such mimicry (or copying), if not left to a creative god’s mysteries, lay in vague, ideal parallelisms or analogies. Darwin’s great breakthrough in the Origin of Species was to show through his mechanism of natural selection how it is that all such cases of exquisite design can be explained naturalistically, as the result of natural selection brought on by the struggle for existence. However, in the first edition of the Origin, Darwin did not take up these problems.