Very striking are those cases of protective resemblance in which the animal resembles in color and shape, sometimes in extraordinary detail, some particular object or part of its usual environment. This may be called _special protective resemblance_. The larvæ of the Geometrid moths called inch-worms or span-worms are twig-like in appearance, and have the habit, when disturbed, of standing out stiffly from the twig or branch on which they rest, so as to resemble in attitude as well as color and markings a short or broken twig. To increase this simulation the body of the larva often has a few irregular spots or humps resembling the scars left by fallen leaves, and it also lacks the middle prop-legs of the body common to other lepidopterous larvæ, which would tend to destroy the illusion so successfully carried out by it. The common twig-insect or walking-stick (fig. 162) with its wingless, greatly elongate, brown or greenish body and legs is when at rest quite indistinguishable from the twigs on which it lies. Another excellent example of special protective resemblance is furnished by the famous green-leaf insect (_Phyllium_) of the tropics, which has broad leaf-like wings and body of a bright green color with markings which imitate the leaf-veins, and small irregular yellowish spots which simulate decaying or stained or fungus-covered spots in the leaf. Most striking of all, however, is the large dead-leaf butterfly _Kallima_ (fig. 163) of the East Indian region. The upper sides of the wing are dark with purplish and orange markings not at all resembling a dead leaf. But the butterflies when at rest hold their wings together over the back, so that only the under sides of them are exposed. These are exactly the color of a dry dead leaf with markings mimicking midrib and oblique veins, and, most remarkable of all, what are apparently two holes like those made in leaves by insects, but in the butterfly imitated by two small circular spots free from scales and hence clear and transparent. When _Kallima_ alights it holds the wings in such position that the combination of all four produces with remarkable fidelity the simulation of a dead leaf still attached to the twig by a short pedicel or leaf-stalk (imitated by a short "tail" on the hind wings). The head and legs of the butterfly are concealed beneath the wings. [Illustration: FIG. 163.--The dead-leaf butterfly, _Kallima_ sp., a remarkable case of special protective resemblance. (From specimen.)]