THE CAUSE OF MIMETIC RESEMBLA.IfCE. 595 



expiinse tlie brown head and legs of the insect were visible just as, 

 in the case of the ant, they appear beneath the piece of leaf which 

 IS carried vertically between the mandibles and thrown over the 

 back. This example was described by the present writer in Proc. 

 Zool. Soe. 1891, p. 462. The appearance of the membracid and 

 leaf-carrying ant is seen in fig, 7, which is reproduced from the 

 paper just mentioned. It is possible that certain species of the 

 Orthopterous genus Tettix (^Acridiidcd) also resemble ants 

 carrying leaves. 



It would of course be ridiculous to ascribe this last resem- 

 blance to any direct external forces connected with locality, or 

 to any internal forces, independently producing a like result, 

 and, as the species was in an immature condition, it is equally 

 impossible to invoke the aid of sexual selection. 



Natural selection remaius as the only feasible interpretation. 



Even more striking than this remarkable example is the con- 

 templation of all these various methods and their relation to 

 each other. The means by which the resemblance to ants are 

 brought about are diverse, the end — the resemblance itself — is 

 uniform. Furthermore, the likeness is almost always detailed and 

 remarkable, however it is attained, while the methods made use 

 of differ absolutely. Such a result, it would seem, is the most 

 complete proof of the operation of natural selection that can be 

 attained, short of the actual demonstration of its action by 

 observation and statistics. If this argument be confirmed by a 

 study and comparison of the foregoing figs. 1 to 7, I venture to 

 think that it will meet with general acceptance. 



When one insect resembles an ant by the superficial alteration 

 of its whole body-form, another by the modification of a shield- 

 like structure which conceals its unaltered body, another by 

 having the shape of an ant painted, as it were, in black pigment 

 upon its body while all other parts are concealed ; another 

 by a further modification of its body, so that it represents not 

 an ant only, but the object which the ant is almost always 

 carryiug, — when the effect of all these results is heightened by 

 appropriate habits and movements, we are compelled to believe 

 that there is something advantageous in the resemblance to an 

 ant, and that natural selection has been at work. The phenomena 

 do not merely disprove all other suggested causes of change, but 

 they constitute the most powerful indirect proof of the operation 

 of natural selection. 



