Chameleon

Chameleon, the common name of one of the three suborders of Lacertilia or lizards. The chief genus is Chamaeleon, containing most of the fifty to sixty species of the whole group, and with the most extensive range, all through Africa and Madagascar into Arabia, southern India and Ceylon. The Indian species is Ch. calcaratus; the dwarf chameleon of South Africa is Ch. pumilus; the giant of the whole tribe, reaching a total length of 2 ft., is Ch. parsoni of Madagascar. The commonest species in the trade is Ch. vulgaris of North Africa, introduced into southern Andalusia. A few queer genera, with much stunted tail, e.g. Rhampholeon, in tropical Africa and Brookesia in Madagascar are the most aberrant. The common chameleon is the most typical. The head is raised into a pyramidal crest far beyond the occiput, there is no outer ear, nor a drum-cavity. The limbs are very long and slender, and the digits form stout grasping bundles; on the hand the first three form an inner bundle, opposed to the remaining two; on the foot the inner bundle is formed by the first and second toe, the outer by the other three toes. The tail is prehensile, by being rolled downwards; it is not brittle and cannot be renewed. The eyeballs are large, but the lids are united into one concentric fold, leaving only the small pupil visible. The right and left eyes are incessantly moved separately from each other and literally in every direction, up and down, forwards and straight backwards, producing the most terrible squinting. Chameleons alone of all reptiles can focus their eyes upon one spot, and conformably they alone possess a retinal macula centralis, or spot of acutest, binocular vision. The tongue has attained an extraordinary development. It is club-shaped, covered with a sticky secretion, and based upon a very narrow root, which is composed of extremely elastic fibres and telescoped over the much elongated, style-shaped, copular piece of the hyoid. The whole apparatus is kept in a contracted state like a spring in a tube. When the spring is released, so to speak, by filling the apparatus with blood and by the play of the hyoid muscles, the heavy thick end shoots out upon the insect prey and is withdrawn by its own elasticity. The whole act is like a flash. An ordinary chameleon can shoot a fly at the distance of fully 6 in., and it can manage even a big sphinx moth.

Another remarkable feature is their changing of colour. This proverbial power is greatly exaggerated. They cannot assume in succession all the colours of the rainbow, nor are the changes quick. The common chameleon may be said to be greenish grey, changing to grass-green or to dull black, with or without maroon red, or brown, lateral series of patches. At night the same specimen assumes as a rule a more or less uniform pale straw-colour. After it has been watched for several months, when all its possibilities seem exhausted, it will probably surprise us by a totally new combination, for instance, a black garb with many small yellow specks, or green with many black specks. Pure red and blue are not in the register of this species, but they are rather the rule upon the dark green ground colour of the South African dwarf chameleon. The changes are partly under control of the will, partly complicated reflex actions, intentionally adaptive to the physical and psychical surroundings. The mechanism is as follows. The cutis contains several kinds of specialized cells in many layers, each filled with minute granules of guanine. The upper cells are the smallest, most densely filled with crystals, and cause the white colour by diffusion of direct light; near the Malpighian layer the cells are charged with yellow oil drops; the deeper cells are the largest, tinged light brown, and acting as a turbid medium they cause a blue colour, which, owing to the superimposed yellow drops, reaches our eye as green; provided always that there is an effective screen at the back, and this is formed by large chromatophores which lie at the bottom and send their black pigment half-way up, or on to the top of the layers of guanine and oil containing cells. When all the pigment is shifted towards the surface, as near the epidermis as possible, the creature looks black; when the black pigment is withdrawn into the basal portions of the chromatophores the skin appears yellow.

The lungs are very capacious, and end in several narrow blind sacs which extend far down into the body cavity, so that not only the chest but the whole body can be blown up. This happens when the animals hiss and fight, as they often do. But when they know themselves discovered, they make themselves as thin as possible by compressing the chest and belly vertically by means of their peculiarly elongated ribs. The whole body is then put into such a position that it presents only its narrow edge to the enemy, and with the branch of the tree or shrub interposed. They are absolutely arboreal, but they hibernate in the ground.

The usual mode of propagation is by eggs, which are oval, numerous, provided with a calcareous shell, and buried in humus, whence they are hatched about four months later. But a few species, e.g. the dwarf chameleon, are viviparous.

Chameleons are insectivorous. They prefer locusts, grass-hoppers and lepidoptera, but are also fond of flies and mealworms. They are notoriously difficult to keep in good health. They want not only warmth, but sunshine, and they must have water, which they lick up in drops from the edges of wet leaves whenever they have a chance. The silliness of the fable that they live on air is shown by the fact that they usually die in an absolutely emaciated and parched condition after three or four months’ starvation.