The earthworm's shape and movements are suited to its habits of burrowing through the soil. Its habits of swallowing the soil fit it for burrowing and for obtaining its food at the same time.
Many insect larvæ, as the tomato worm and the cabbage-worm, are of the same colour as the plants on which they feed, and this enables them to escape detection by birds.
The larvæ of dragon-flies and May-flies breathe in water by means of gills very much as fishes do, but the adult forms are suited for breathing in air.
Female birds are usually dull gray or mottled, so that their colours blend with their surroundings while they are nesting, and hence they do not attract the notice of their enemies.
Birds that swim have webbed feet, which act as oars for pushing them through the water. Their feathers are compact and soft for warmth, and these properties, together with oil on their surfaces, make them waterproof.
The tongue of the woodpecker is long, spear-shaped, and sticky; hence it is adapted for catching insects in the holes pecked into the wood.
The tongue of the toad is fastened at the front end, so that a flap can be shot out for more than an inch in front of the animal, thus enabling it to catch insects on its sticky surface.
The toes of the frog are webbed to make them more serviceable in swimming.
The tail of the musk-rat is strong and broad like the blade of an oar and serves the same purpose as an oar.
The tail of the fish is more serviceable for swimming than legs would be.