532 THE POPULAR SCIENCE MONTHLY 



variable as color, that, therefore, concealment is most easily obtained by 

 color modification. Protective resemblance in all its manifold forms 

 has ever been dominant in his mind as a greater principle than that of 

 the sexual selection of color which Darwin favored. 



Here may be cited Wallace's own account of his famous observation 

 of mimicry in the leaf butterfly from his volume of 1869, " The Malay 

 Archipelago " : 



The other species to which I have to direct attention is the Kallima paraleMa, 

 a butterfly of the same family group as our Purple Emperor, and of about the 

 same size or larger. Its upper surface is of a rich purple, variously tinged with 

 ash color, and across the fore wings there is a broad bar of deep. orange, so that 

 when on the wing it is very conspicuous. This species was not uncommon in dry 

 woods and thickets, and I often endeavored to capture it without success, for after 

 flying a short distance it would enter a bush among dry or dead leaves, and how- 

 ever carefully I crept up to the spot I could never discover it till it would sud- 

 denly start out again and then disappear in a similar place. At length I was 

 fortunate enough to see the exact spot where the butterfly settled, and though I 

 lost sight of it for some time, I at length discovered that it was close before my 

 eyes, but that in its position of repose it so closely resembled a dead leaf at- 

 tached to a twig as almost certainly to deceive the eye even when gazing full 

 upon it. I captured several specimens on the wing, and was able fully to under- 

 stand the way in which this wonderful resemblance is produced. . . . All these 

 varied details combine to produce a disguise that is so complete and marvellous 

 as to astonish every one who observes it; and the habits of the insects are such 

 as to utilize all these peculiarities, and render them available in such a manner 

 as to remove all doubt of the purpose of this singular ease of mimicry, which is 

 undoubtedly a protection to the insect. 



In 1867, in a manner which delighted Darwin, Wallace advanced his 

 provisional solution of the cause of the gay and even gaudy colors of 

 caterpillars as warnings of distastefulness. In 1868 he propounded his 

 explanation of the colors of nesting birds, that when both sexes are con- 

 spicuously colored, the nest conceals the sitting bird, but when the male 

 is conspicuously colored and the nest is open to view, the female is 

 plainly colored and inconspicuous. His theory of recognition colors as 

 of importance in enabling the young of birds and mammals to find their 

 parents was set forth in 1878, and he came to regard it as of very great 

 importance. 



In "Tropical Nature" (1878) the whole subject of the colors of 

 animals in relation to natural and sexual selection is reviewed, and the 

 general principle is brought out that the exquisite beauty and variety of 

 insect colors has not been developed through their own visual percep- 

 tions, but mainly and perhaps exclusively through those of the higher 

 animals which prey upon them. This conception of color origin, rather 

 than that of the general influence of solar light and heat or the special 

 action of any form of environment, leads him to his functional and 

 biological classification of the colors of living organisms into five groups, 

 which forms the foundation of the modern more extensive and critical 

 classification of Poulton. He concluded (p. 172) : 



