The common frog attains a length of three or four inches.[66] He has glandular ridges down the skin of his back, and these, with his colors, singularly fit him for his home: the darker ridges imitating plant-stems; the green coat, leafage; the silver vest, the glimmer of water; the brownish feet and markings, the moist earth; while the yellow markings add to the protective display, in being like the stamens and pistils of surrounding flowers, and of the hue of many buds and blossoms. Thus the frog in his native haunts is protected by his garments, and is little likely to be seen unless he moves, or is betrayed by his full, bright eyes or the palpitations of his breast. While the common frog represents the aquatic Ranidæ, his cousin, the wood-frog, represents a branch of the widely distributed family which prefers dry dwellings, except in the breeding season, when the eggs must be deposited in water. The wood-frog is smaller than the bull-frog, and is dressed in olive-green and shades of brown, like the colors of dead leaves and dry twigs. There is a large black patch on the side of the head around the big ear-drum. The wood-frog takes such enormous leaps that it is very difficult to catch. It is shy, and makes a prodigious jump at the first hint of danger. When it drops to the ground it is scarcely discernible from the dry vegetation about it. The wood-frog maintains the moisture of its skin by hiding in damp moss or in decayed logs, and in little hollows in the ground. It avoids the sunshine, and keeps close to the earth. The tree-frog is another curious frog. Smaller than its cousins, it is dressed in bright green, spotted with black, and has a membrane stretched between its toes, which gives its feet a broad, flat surface, and helps to sustain it as it leaps from branch to branch, somewhat in the fashion of a flying squirrel. In tropical lands, where many trees are decked with gorgeous blossoms, tree-frogs appear very gaily colored, the splendor of the coat being protective in such surroundings. The swamp-frog is dressed in black and light brown, and lives in marshes in the Eastern United States. Its voice is a prolonged croak. The clamata, or “bawling-frog,” lives about cold, damp springs, and is very noisy. The resounding roar of the bull-frog is a well-known sound. No wonder that Horace, the Roman poet, wrote that “the noisy frogs from the marshes drive away sleep.” Cats, geese, owls, vultures, hawks, otters, and other creatures eat frogs, and the luckless creatures can hardly appear without finding an enemy. To balance this destruction of their forces they produce great numbers of eggs. When tadpoles first reach the frog state they are black. I have seen hundreds of them together, so that the pond mud seemed alive and crawling. FOOTNOTES: [63] Frogs and toads sometimes squeal or cry with pain or terror. [64] As these animals respire also through the skin they may live sometime without breathing through the nostrils.