The insects whose very existence, in some cases, depends upon trees, are innumerable. What, for example, would become of the larvae of the cicada, or locust, which, in the cold and darkness of their subterranean life, for seventeen years suck the juicy roots of trees; or the caterpillars of the moths, spinning high their webs among the leaves; or the countless beetles whose grubs bore through and through the trunk their sinuous, sawdusty tunnels; or the ichneumon fly, which with an instrument--surgical needle, file, augur, and scroll saw all in one--deposits, deep below the bark, its eggs in safety? If forced to compete with terrestrial species, the tree spiders and scorpions would quickly become exterminated; while especially adapted arboreal ants would instantly disappear. We cannot entirely exclude even fishes from our list; as the absence of mangroves would incidentally affect the climbing perch and catfishes! The newts and common toads would be in no wise dismayed by the passing of the trees, but not so certain tadpoles. Those of our ditches, it is true, would live and flourish, but there are, in the world, many curious kinds which hatch and grow up into frogs in curled-up leaves or in damp places in the forks of branches, and which would find themselves homeless without trees. Think, too, of the poor green and brown tree frogs with their sucker feet, compelled always to hop along the ground! Lizards, from tiny swifts to sixty-inch iguanas, would sorely miss the trees, while the lithe green tree snakes and the tree boas would have to change all their life habits in order to be able to exist. But as for the cold, uncanny turtles and alligators,--what are trees to them! In the evolution of the birds and other animals, the cry of "excelsior" has been followed literally as well as theoretically and, with a few exceptions, the highest in each class have not only risen above their fellows in intelligence and structure, but have left the earth and climbed or flown to the tree-tops, making these their chief place of abode.