Romanes, Animal Intelligence, pp. 361, 362. ------------------------------------------------------------------------ CHAPTER XIX Natural selection—Protective resemblances—A locust’s stratagem—Mock leaf-cutting ants—Flowery dissemblers—A Malay explanation—Snake-suggesting caterpillars—A prudent lizard—Inconclusive experiments—A bogus ant—Flies that live with bees—A caterpillar that dresses up—A portrait-modelling caterpillar. EVERYBODY knows nowadays how all the different species of animals and plants, living and extinct, have come into existence. It was quite simple. All they had to do was to keep on varying. Some of them varied in a way that was good for them, some in a way that was bad. The latter died, but the others increased and multiplied, and as the process was always going on, and it is impossible to vary long without becoming changed, it happened that creatures which had started with a certain appearance got in time to have quite another one, so that they would not have been recognised by the people who used to know them, if these same people had kept alive. However, as the process was so slow that it took millions of years, and is still going on, awkward things of this sort never happened, and so, as nobody had ever seen one species of animal change into another before their eyes, they found it difficult to believe that they ever had done so; for the ordinary person says “seeing’s believing,” though he believes in all sorts of things that neither he nor anyone else ever has seen, or is ever likely to. Still, for all that, he thinks his own eyesight must be better than anyone else’s. This process of eternal change, with the changes for the better surviving, and those for the worse dying out, is what is called natural selection, and if we understand it—as there are few now who do not—we can understand this, that if any kind of creature is so strong and formidable that it would be an advantage for weaker creatures to be mistaken for it, then it is not at all unlikely that some of these weaker creatures will get more and more to resemble it, until at last they are so mistaken. For instance, our common wasps, who are armed with a formidable sting, and are very skilful in using it, are not attacked by any other insect, excepting hornets, which are not common. Any fly or moth, therefore, that resembles a wasp will be generally left alone, and the more so the more it resembles it. Accordingly we do find flies and moths that look very like wasps, and live safely in consequence. Still more would it be of advantage to look like a hornet, and there is a moth so like one that it is called the Hornet-clear-wing.