Page:Popular Science Monthly Volume 75.djvu/562

556 being, as in the case of the butterflies A and B, midway between the extremes, favored by the momentary illumination's being neither too great nor too small. Even in the climaxes of conspicuousness his patterns still perpetually lessen his visibility in direct ratio to their strength. And when he is chased by an enemy every instant of confusion as to where he leaves off and the background begins must often save him, so that the brighter his light marks and the deeper his dark ones, the greater the range of background" he can meet without silhouetting as an entirety, and being for the instant conspicuous. One advantage which patterns do certainly sacrifice in purchasing the above advantages is that, although their Wearer is never seen entire until the background is too dark for his black, or too light for his white, yet it is true that, on the other hand, some note of a pied costume is always to be detected moving when the wearer moves. In this respect, monotone, whenever at rare moments it exactly matches its background, has the advantage. This fact additionally condemns the aerial animal to detection when he moves, yet it is often rather his motion than his form that becomes noticeable, because each of his patterns still has the chance of passing for something beyond him.

Fig. 7 shows one of the cardinal effects of patterns. C is a bird patterned in white, black and gray. Seen against the sky he loses his white part—against the dark he loses his dark part—and against the gray, his gray part.

Now when we find that pattern works always for concealment in direct ratio to its own conspicuousness and elaboration, there remains no vestige of evidence that the specific recognizability of the of course constant pattern of each species has had, even to the slightest degree, a hand in the evolution of such pattern. And those who would still claim for conspicuous patterns any other reason for being than concealment of their wearer must first show what patterns could in the slightest degree better serve procryptic ends, under the circumstances, than the very ones now in use; and also what ones would less aid identification.

There are two groups of supposed warningly-colored animals that seem particularly to lend themselves to the exposure of the weakness of