356 THE POPULAR SCIENCE MONTHLY. 



some animals such as the leaf-insects and walking-stick insects to 

 the extent of close and actual mimicry, our surprise is increased. 



Or, lastly, when we find, as in the latest phase of modern warfare, 

 that the concealed torpedo is used as a subtile and powerful means 

 for effecting the destruction of whole fleets, the fact cannot but call 

 to mind the electrical apparatus of some fishes and notably that of 

 the torpedo or electric ray which exists as a natural means of de- 

 fense, the powers of which, few, if any, of their less favored neigh- 

 bors care to test or provoke. 



While the consideration of the more prominent and typical means 

 of defense in animals may very reasonably occupy our brief atten- 

 tion, a few words on the subject of mimicry in the animal series may 

 also prove interesting, more especially as this form of protection, 

 through imitation of their surroundings, forms a simple yet effective 

 means of defense to many organisms. We have already referred to 

 the readily-perceived and very general correspondence in color seen 

 throughout the animal world between animals and their abodes ; and 

 of the more general aspects of this condition nothing further need be 

 said. The more special and striking developments of mimetic resem- 

 blances are found in cases in which not merely the general color of 

 their environments is imitated, but where resemblances of a close, and 

 sometimes of a very extraordinary kind, to other animals, to plants, or 

 even to inorganic objects, are to be noted. In the leaf-insects, which 

 are included in the same order as locusts, crickets, etc., for example, 

 the wings are not only colored to resemble leaves, but their struct- 

 ure imitates in the most exact manner the appearance of the veins of 

 the leaf. Nor does the principle of imitation end with this sufficiently 

 remarkable effect. In some leaf-insects the colors of the leaf-like 

 wings actually change with the season of the year ; as if in the most 

 perfect sympathy and harmony with the alteration of colors in the 

 actual leaves. And the mimicry becomes of still more perfect kind, 

 to our thinking, when we find that the wings of the leaf-insect exhibit 

 even the characteristic markings we are familiar with in leaves as pro- 

 duced by the attacks of minute insects ; Nature thus imitating, not 

 merely the natural structure of the leaf, but the very imperfections to 

 which the leaf is subject. It has been suggested that the little leaf- 

 eating insects may be themselves deceived by the mimicry of their 

 larger neighbors, and may actually eat into the wings of the latter, 

 and thus produce the eroded appearance. But, if this latter view be 

 correct, it only makes out a stronger case for the perfect reproduction 

 of the leaves in the wings of the insect. Mr. Wallace has given us 

 a very typical example of another such case of the imitation, not 

 only of leaves, but of the natural parasites of leaves, in a butterfly, 

 the wings of which, on their under-surfaces, resemble leaves ; while 

 the imitations of decay of leaves and of the fungi that appear thereon 

 are so close that, as Mr. Wallace remarks, " it is impossible to avoid 



