A strange characteristic of most lizards with slender tails is the power to part with them at a moment's notice. If an enemy seizes this appendage, which often is held temptingly aloft, it breaks off and its owner escapes before the would-be captor has had time to recover from his surprise. Within a short time a new tail is developed, but it is never so perfect as the original organ.
Most lizards lay eggs, few in number, and with shells hard in some families, parchmentlike in others, that are hidden in a hole in a dead stump or some similar place of concealment, and are left to be hatched by the warmth of the sun. Many lizards retain their eggs until nearly ready to hatch, and so are practically viviparous. The embryos have an "egg tooth," as do turtles and snakes.
The Lacertilia are naturally divisible into three sections, namely, geckos, typical lizards, and chameleons.
The geckos are a large and ancient family represented in all tropical countries, and some species are common along both shores of the Mediterranean, but none reach the United States. They are small, plump, flat-headed, and mostly somber in color, but this is changeable; the skin has a granular surface, but regular scales cover the desert-dwelling species. One peculiarity of the group is the adaptation of the foot to the habit of climbing about rocks and trees. The undersurface of the toes has a series of plates, which serve as adhesive pads wherewith the animal is enabled to climb not only trees and the smooth rocks, but a windowpane or to run along the ceiling with the ease of a fly. Another peculiarity is the fact that the eyeball is covered by a "watch glass" of transparent skin, under which the little animal rolls its eyes and stares at you with vigilant interest. Geckos are nocturnal in habit, and as evening approaches come out from their retreats and become active in hunting for insects, and in avoiding the other lizards, snakes, and so forth, that would like to seize and eat them; and it is then that are heard their low, two-syllabled, clucking calls that give them the name "gec-ko." These funny little lizards are utterly harmless, come into houses, and are easily tamed, yet are regarded in many countries with superstitious dread and that foolish fear of poison that is attached to most small lizards and newts. In the Orient several strangely modified forms exist.
The lizards proper (Lacertæ) number several hundred species classified in eighteen families, and differ vastly in size, shape, food, and place and manner of life. Some, like the degraded slowworms, are limbless, scaleless and in their serpentine form and underground life resemble worms more than anything else. Others, such as the "flying dragons" of Malayan forests, have developed great winglike expansions of the skin on the sides, folded close to the body as they climb about the trees, but capable of being spread as supports when they wish to take a long gliding leap to some distant perch; and an Australian species has similar skin expansions that can be raised into a broad ruff around the neck that gives the little animal a terrifying aspect. The many kinds that live in deserts have the dull hue of the ground, or may bristle with spines, of which the squat "horned toad" of California is an excellent example; while those that scamper about the trees and rocks of the equatorial region are often brilliantly striped or spotted in reds, greens and blues. Many are pugnacious and able to bite severely, but the only one whose bite is poisonous is the heloderma of the Mexican border. This is a fat, sluggish, black and yellow creature, about a foot in length, that inhabits the hot desert sands. Fortunately it is slow to anger, but when it does bite there flows into the wound a poison which has the same effect as the venom of the rattlesnake, although less copious and virulent. Severe illness, and in a few cases death, have resulted from the bite of this ugly creature, which is more commonly known as the "Gila monster," because it is prevalent in the valley of the Gila River in southern Arizona.
As the great family Agamidæ is confined to the Old World, so the Iguanidæ belongs to America, where several species are numerous in the tropics, and reach a size of three to five feet, much of which is tail. They live in trees, feed on vegetation, and haunt the banks of rivers into which they jump on the slightest alarm. One traveler relates that along the Mosquito Coast of Nicaragua, when a person is going in a canoe up some of the narrow, unfrequented creeks, he encounters quite a shower of iguanas, and runs some risk of getting his neck broken, for a big iguana will weigh twenty-five pounds or more. Their flesh, resembling that of chicken, is a favorite article of food and iguanas are constantly brought to rural markets. The family contains about 300 species. Among them is the common little "chameleon" (Anolis) of our Gulf States, so often sold to tourists as a curiosity, and brought north to die of cold and neglect. It is golden green on the upper surface, and white on the under, and the throat, when inflated, glows with vermilion; it is a harmless, active little tree dweller, and will change its colors to suit its surroundings with astonishing rapidity. In another genus (Sceloporus) is placed the blue-tailed, variable, "fence lizard," or "swift," which is known throughout the eastern United States; but the common small lizards of the Pacific slope belong to Gherronotus and other genera.
The largest lizards of all belong to the two families Varanidæ, the "monitors" of Africa and eastward to Australia, and Teidæ, the "tejus" of Central and South America. They are singularly alike in appearance and habits—long-tailed, slender, smooth-skinned, carnivorous creatures, living in all sorts of places, varying with the numerous species, and both hated and utilized by the natives of the various countries they inhabit. Some monitors are more than seven feet long. The American tejus, such as the big "teguexin" of Brazil, frequent forests and plantations, where their strength and speed enable them to catch all kinds of animals, from insects to worms, frogs, snakes, mice, and birds. "They take chickens and eggs from the farms, and they are frequently hunted down by dogs for the sake of their flesh, which is considered good to eat. They defend themselves with lashing strokes of their long tail and with their powerful jaws."
The chameleons differ so much from other lizards that they have been placed by some systemists in a different suborder. The chief differences are three. First, the feet, terminating rather long legs, have the fingers and toes so arranged that two digits oppose three as do our thumbs the palm of the hand, and the animal can grasp a branch just as we would, giving so firm a grip that chameleons are exceedingly agile climbers, and may take as many odd attitudes among the branches as would a monkey. Second, the eyes are very large, but the eyelids have grown together over them, leaving only a small hole out of which to look. The right and left eye roll about incessantly, and independently, giving a most comical squinting effect—but no lizard sees with both eyes at once! Third, the tongue has reached an extraordinary development. When the mouth is shut it is withdrawn into a tubular sheath at the back of the mouth; but when a fly is seen and wanted it is shot out like a released spring, seizes the fly in the flaps at its club-shaped extremity, and is quickly withdrawn. This tongue may be thrust out to a distance equal to the length of the body, less the long, tapering, prehensile tail, which is another important part of the equipment of these active tree dwellers. The skin is not scaly, but granular in appearance; and the skull is prolonged behind into a pointed helmetlike form that is distinctive of the group.
Chameleons are most celebrated, however, for their remarkable power of changing their color, but this is by no means always, or perhaps often in direct response to the hue of their immediate surroundings. Dr. Hans Gadow has made an extensive study of his captive specimens of the common chameleon of the Mediterranean region, and confesses himself baffled in the attempt to learn an explanation of the influences, external or mental, that causes the alterations of hue. One judges from his observations that they are mainly the expression of fleeting emotions—but who can read the emotions of a lizard?