Page:Popular Science Monthly Volume 75.djvu/555

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551
THEORIES OF MIMICRY

The universal tendency of common habits and environment to be accompanied by common form and appearance has long been a familiar fact, and no one would have conceived of a vast gap in this tendency but that naturalists thought themselves forced to accept the evidence that such a gap existed, and set themselves to work to fill it as best they could. Now, however, the obstacle to their discovering the wholly concealing character of the whole array of costumes that had puzzled them vanishes, and no power can withhold this array from taking its place in the ranks of universal procryptic coloration.

The following pages demonstrate that all diversification of the colors of animals' costumes tends wholly and unmixedly to conceal them. This should set the believers in conspicuous species reflecting that while they are making their records of cases of momentary conspicuousness of individuals of one species or another, they are making no investigation whatever of the possibility that all the while a large number of individuals of this same species are, through some magic of their costume, escaping their sight and making no impression on their minds. It is precisely to such an investigation as this that I here invite the reader.

Any out-of-door naturalist knows that if he walk through a sunny field of fairly profuse vegetation, after first studying it, say, from an upper window, he will flush an immensely greater amount of so-called conspicuous aerial life than he had detected from the window, and he will believe that much of this life was all the time within the field of his vision.

These plates have been prepared with the especial purpose of exposing the weakness of the optical hypotheses upon which the theories of "warning-colors," "recognition," "mimicry," etc., so largely rest. They show that these hypotheses would never have lived a day had their originators begun by testing them. Darwin's erroneous supposition that a conspicuous mark on an object makes the object itself conspicuous has been built on and rebuilt on by the leaders of zoological research, even down to the present day. Entomologists, especially, make much of the supposed power of sharp and strong patterns to render conspicuous that particular part of the insect which they occupy. We now discover that the effect of these patterns is the very opposite. In the illustrations of this article we see the actual effect of such marks in several typical situations. Fig. 1 shows two butterflies and several letters, all of one color, and against one background. On each butterfly and on several of the letters bright spots or patterns have been painted. As the spectator recedes, those parts of the butterflies nearest the bright patterns fade, until, at a short distance, they are invisible, while the rest of the insect is clearly distinguishable up to a much greater dis-