Chameleon

Chameleons are a clade of small-to-medium-sized lizards of the family Chamaeleonidae. They are famous for their ability to change colors, but the truth is that not all have the ability. Chameleons are also famous for their long, sticky tongue, and their eyes that can cover a full 360-degree arc of vision around their body. The English word “chameleon” is derived from the Latin chamaeleo which is borrowed from the Greek χαμαιλέων (khamaileon), a compound of χαμαί (khamai) “on the earth, on the ground” + λέων (leon) “lion”. The Greek word χαμαιλέων (khamaileon) is a calque translating the Akkadian nēš qaqqari, "ground lion".

Anatomy
Chameleons have anatomy that distinguishes them from their lizard cousins. They are the only lizard with zygodactyle feet which allows them to climb trees. Their feet are split into two main fingers with a soft pad in between. An interesting fact about chameleon’s feet is that they have two claws on the outside of their front foot and three on the inside, yet the situation is reversed in their back foot. Since the eyes of a chameleon can rotate and focus separately, they can cover a full 360-degree arc of vision around their body, which makes it easier for them to catch their prey. They can also focus on one object which gives them stereoscopic vision. They are also famous for their sticky long tongues. The tongue has a sticky tip on the end which will make it impossible for prey to escape. Once the tongue sticks to the prey, it is pulled back to the mouth where the chameleon’s strong jaw crushes and consumes them. 

Reproduction
Chameleons look out for other chameleons only during the late summer which is the breeding season. Chameleons lay eggs after 3 to 6 week gestation, their eggs are fertilized internally. A female finds a warm spot at the base of a tree when she is ready to lay her eggs. When she finds the warm spot, she begins to dig 4-12 inches depending on the species. Commonly they lay up to 30 eggs, but some extraordinary chameleon species such as Small Brookesia species only lay 2-4 eggs. The size of clutch varies greatly even among the same species. Eggs generally hatch after 4-12 months after they are laid, but some unusual species are known to hatch 24 months after they are laid. 

Diet
With eyes that can cover a full 360-degree arc of vision around their body and sticky long tongue, chameleons can easily catch their prey. When captured by the sticky tip on the end of the tongue, there is no hope for prey to escape from the chameleon. Once the tongue sticks to the prey, it is pulled back to the mouth where the chameleon’s strong jaw crushes and consumes it. Chameleons generally eat locusts, mantids, crickets and other invertebrates, such as snails and spiders. However, larger chameleons may also consume vertebrates like lizards and small birds that are within their prey-size range. A few wild chameleons, such as Chamaeleo calyptratus have been also reported to eat flowers, leaves, berries, fruit and other living or dried organic matter.

The color change
Chameleons are known to change colors due to their background, but the truth is that actually mood, light, and temperature also affects the chameleon to change colors. The secret to how chameleons can change color is because they are born with special cells that are called chromatophores. The top layer of chromatophores, called xanthophores and erythrophores, has red or yellow pigment. Below the top layer, another layer, called iridophores or guanophores, has blue or white pigment. When these pigment cells are commanded to shrink or enlarge from the brain, the skin color of the chameleon changes. There is a layer of dark melanin containing melanophores even deeper under the iridophores. The melanophores affect the 'lightness' of the reflected light of the skin of the chameleon. By the work of these layers in chromatophores, chameleons can change colors. 

Related References

 * Chameleon by multiple authors. Wikipedia.
 * A Truly Bizarre Lizard Christopher J. Raxworthy. Madagascar.
 * Chameleon Columbus Zoo and Aquarium.
 * Chameleons Sharon Katz Cooper. National geographic.
 * Introduction Michael Fry. CIN.