Many living beings in order to protect trying to buy the similarity with other objects, plants or even animals that have a high degree of protection (for example, poisonous or disgusting to the taste). Most often such masking occurs in insects.
So, stick insects are indistinguishable from dry twigs and wood bugs are often painted to match the color of the bark of trees on which they live. South American grasshopper is very similar to green leaf. Many caterpillars are also protected by a bright green color, making them invisible to birds.

The stick is not easy to distinguish from the branch on which he sits
Many examples of masking the color of the environment among birds and animals. Often they are painted in harmony with their place of residence. So, many Arctic animals have a white color, which hides them in the snow (Arctic Fox, polar bear, snowy owl), and desert animals often dyed in a sand color.
Protective coloration, which makes the animal less noticeable on the background of its habitat, is called cryptic coloration. If predators cryptic coloration helps to quietly watch the victim and sneak up to it, the victims, on the other hand, cryptic coloration helps to hide from enemies.
The cryptic coloration in the animal world

Flower spider

Fox

The pup - pup

Sandy-grey colour DROMEDARY

Cheetah

Owl

Seahorse in corals

Orchid mantis

Wood moth on the tree bark
Probably everyone knows about hares, whose grey colour for winter changed to white. The same thing is happening to Arctic foxes, ermine.

Ermine in summer and winter
Imitation of other species or environmental conditions is called mimicry.
Mimicry is not the only color. There is a mimicry of the form. One of the examples of mimicry form you have read is a stick. Another example is the butterfly callide from South-East Asia. They have a beautiful brightly coloured wings, but only on the top side. When folded they look like a dried leaf.

Butterfly collide with folded wings
Another type of mimicry is the imitation of other animals or plants. Thus, the number of insects that are able to emit toxic or corrosive substances, has a bright warning coloration, as if saying, "don't touch, poisonous!" Usually the enemies of these insects only need one or two attempts to eat them, to learn the lesson and in the future to avoid them. Next to such insects are other types of insects, whose protection is not poisonous, but they copy the bright menacing look "protected" counterparts, and therefore enemies fear them alone. So, butterflies are heliconid living in Brazil, absolutely unpalatable to birds. And quite tasty butterflies-butterflies survive, because you have acquired very similar to heliconid color of the wings.

Poisonous butterfly Heliconia and imitating her butterflies
However, species-simulators need to maintain the population at this level, so they do not become larger than those insects, which they copy - otherwise cryptic coloration will cease to be a hoax. Usually the number of individuals of a species-simulator many times higher than copying.

Poisonous coral snake and laboatory false coral snake
Mimicry under the poisonous fellow is found not only in insects. So, blind nettle is very similar to stinging nettle, but it has no stinging hairs.

Deaf nettle (white dead-nettle)
very similar to stinging nettle
Found this kind of mimicry, as sound imitation. For example, rabbit owl, which lives in the burrows of rodents, is able to simulate the hissing of a snake.
Even the imitation of smell occurs in nature! The largest on the planet flower - rafflesia - smells very unpleasant: rotten meat! This "flavor" attracts flies, which are looking for a place to lay eggs, and as a result of this small trick pollinate the rafflesia.

The largest flower in the world - rafflesia -
smells like rotten meat.