CH. X.- NATURAL SELECTION: 29 



damage occAsioned by it be more than compensated by some 

 utility not hitherto detected. Prof. Shaler's hypothesis, how- 

 ever, suggests the possibility that this whole speculation is 

 fundamentally erroneous. Far from being injurious to the 

 snake, by serving to warn its prey, it would appear that the 

 rattle may be directly useful by serving as a decoy. Prof. 

 Shaler has observed that the peculiar sound of the rattle is a 

 very close imitation of the note emitted by a certain cicada 

 common in American forests frequented by rattlesnakes; and 

 according to his ingenious suggestion, the bird, hearing the 

 note and thinking to make a meal of the cicada, advances 

 upon its own destruction, becoming the eaten instead of the 

 eater. If this be true, there may be data here for explaining 

 some of the alleged phenomena of fascination, so far as 

 rattlesnakes are concerned ; and another case will be added 

 to the numerous cases now on record in which certain 

 animals have acquired, for utility's sake, peculiarities charac- 

 teristic of totally different species. I should be more inclined, 

 however, to adopt quite a different interpretation of the 

 rattlesnake's rattle. As hinted above, the general law that 

 animals are benefited by concealment has some important 

 exceptions. In many cases, when an animal is especially 

 noxious, it is for his advantage to be conspicuous, that 

 enemies may recognize him at a distance and keep away 

 from him. Thus, as we have seen, while grasshoppers, moths, 

 tnd butterflies (on the exposed under-surfaces of their wings) 

 are usually so coloured as best to escape notice, on the other 

 hand, bees and wasps, which are protected by their stings, 

 and many beetles, which are protected by a noxious taste or 

 odour, are apt to be conspicuously coloured. And the jet- 

 black toad of La Plata is a still better example. Now a 

 i.'attlesnake is unquestionably a very noxious animal, and so 

 dangerous to its enemies that they will always do well to 

 keep out of its way. Moreover, the death-wound inflicted 

 by it, though usually very sure, is somewhat slow in operation; 



