On this same principle of being mistaken for something that is safe from attack or annoyance, all sorts of animals, and in a special degree insects, have come to look like various objects around them, and amidst which they live, such as stems of grass, pieces of moss or stick, leaves, flowers, and so on—some of the resemblances being more special and extraordinary. These are things which, though the eye may see, it does not as a rule dwell upon, because there are so many others round about. Who, for instance, would look at any particular blade of grass? So a bird that would pounce down upon an insect that it saw moving amongst the leaves of a tree, if there was no doubt that it was an insect, would not take any pains to examine what only looked like one leaf amongst many. Thus, throughout nature we have these curious resemblances of certain creatures to certain other creatures, or to the plants or inanimate objects around them, but it is principally amongst insects that the phenomenon is met with, probably because they increase and multiply so quickly that there has been more time both for the laws of inheritance and for the great controlling one of natural selection to have come into play. Whatever is the reason, there is no doubt about the fact, which will be best illustrated by one or two salient instances. Ants, though they fall a prey to various animals larger than themselves—such as birds or ant-eaters—yet in their relations with other insects occupy a position of comparative safety, on account of their weapons and pugnacity, and, still more, of their numbers. The driver ants of equatorial Africa, and their South American representatives, the _ecitons_, are indeed, when they set out on their foraging expeditions, the terror, not only of insects, but of all animal life. “Wherever they move,” says Bates, referring to the latter, “the whole animal world is set in commotion, and every creature tries to get out of their way.”[91] This, however, as they climb trees, and send out encircling columns which enclose a considerable extent of ground, is difficult, or rather, impossible, for all such as cannot fly some distance without alighting; for if an ant or two once seize upon them all is over. An insect, therefore, that cannot evade the onset of such an enemy is lucky if it has some such means of ensuring its safety as has been above referred to. One at least thus specially favoured inhabits Nicaragua. “I was much surprised,” says Mr. Belt, “with the behaviour of a green leaf-like locust. This insect stood immovably amongst a host of ants, many of which ran over its legs, without ever discovering there was food within their reach. So fixed was its instinctive knowledge that its safety depended on its immovability, that it allowed me to pick it up and replace it amongst the ants without making a single effort to escape. It might easily have escaped from the ants by using its wings, but it would