Rainbow nature: the glory of green

For animals, it's a complicated colour to produce using pigments.

Many of the birds, reptiles and fish we see as green actually use a combination of yellow and blue pigments and microscopic skin structures.

Despite the effort involved, a fresh and leafy green is a popular colour in the animal kingdom - perfect for a life spent hiding in vegetation.

Explore how and why these nine organisms create their glorious green tones.

Sloth (Bradypus variegatus)

Although sloths are often cited as the only green mammal, they are not truly green: their fur is coloured by algae that are hitching a lift.

Specially adapted grooves or irregular cracks in the structure of a sloth's long fur strands allow algae to cling to its body.

The relationship may be mutually beneficial. Scientists think the algae help to camouflage the sloth in its treetop home, and in return the fur provides shelter and easy access to water.

The animal's body becomes a small ecosystem, hosting a variety of insects that thrive among the algae.

Emerald green tree snail (Papustyla pulcherrima)

The vibrant colour of this shell is part of the reason its owner is endangered.

It became popular among shell collectors and jewellery makers in the 1930s, resulting in the export of large numbers of shells from Manus Island, Papua New Guinea.

The snail was the first invertebrate listed on the Endangered Species Act of the United States of America, and trade of the shells has been controlled since 1975.

It's a rare example of a land snail with green shell pigmentation.

Emerald cockroach wasp (Ampulex compressa)

Glittering metallic green and blue, with red on some of its legs, this wasp is a far cry from its plainer yellow and black cousins.

This species is called a cockroach wasp because it is a parasite of the common household cockroach. A female wasp stings the cockroach and lays an egg on its abdomen. Once hatched, the larva feeds on the cockroach. 

The iridescence is created by light refracting through the layered structure of the wasp's exoskeleton.

Green pigment is very rare in wasps and is almost entirely restricted to species in Chile and Madagascar.

Eclectus parrot (Eclectus roratus)

Eclectus parrots are an extreme example of sexual dimorphism - when males and females of the same species look different.

Males have green plumage with red or blue tail and wing feathers, while females have a deep purple and red outfit.

This strong difference between the sexes is so rare in the parrot family that nineteenth-century biologists mistook the colourful eclectus parrots for two separate species.

The birds have no green pigment in their feathers, but they appear green to us through a combination of yellow pigment and a process of light scattering called the Tyndall effect.

Light hits miniscule structures in the feathers, and short blue wavelengths are scattered most. The combination of the reflected light from the yellow pigment and blue structural colour appears green to our eyes.

Plants

Nearly all leaves contain chlorophyll, as do some other parts of plants. This green pigment helps plants trap light for photosynthesis.

Chlorophyll's colour is secondary to its ability to convert sunlight into chemical energy. It serves a vital function - and it also happens to be green, giving plants their distinctive colour.

This is because chlorophyll absorbs long, red wavelengths and short, blue wavelengths of light, but reflects the green.

Green Moray eel (Gymnothorax funebris)

Living among reefs all over the world, this species is one of the largest moray eels at 1.8 metres long on average.

Its ghostly colour is due to a yellow mucous that covers the creature's blue skin.

The mucous protects against parasites and bacteria. Both the green colour and the speckled areas on the eel's skin provide extra camouflage on the sea floor.

Camouflage even extends inside the eel's mouth, which opens and closes to keep water moving over its gills.

Veiled chameleon (Chamaeleo calyptratus)

Green is the perfect colour for a camouflaged life in the treetops.

Young veiled chameleons are pale green and develop bold bands of colour as they grow, including gold, green, blue, yellow and orange.

The males are more colourful than the females, but both can change hues when they are stressed or looking to attract a mate.

Green lynx spider (Peucetia viridans)

These spiders move from plant to plant on long, spiky legs.

Decorated with black spots, their slightly translucent bodies blend seamlessly into the environment.

They sometimes have a pink or red tinge on their legs. Like chameleons, the spiders can change colour to camouflage themselves against different plants.

The spider sometimes turns a pale yellow colour as it ages - a sign that the green pigment in its body is degrading.

Southern green shieldbug (Nezara viridula)

A green shield-shaped body and a tendency to emit a strange smell help distinguish this bug. Other colour forms exist but they are less common.

Adults grow to about 12 or 13 millimetres in length.

Despite its size, the southern green shieldbug can wreak havoc. It attacks food crops, making it an economic threat in many tropical and subtropical countries.

The bug's piercing mouthparts puncture and damage plants, slowing or even stopping growth, and allowing bacteria inside the fruit.

Crops affected include soya beans, cotton, avocado, sweet potatoes, rice and tomatoes.

The bug has spread across the world, and was first recorded in the UK by a Museum scientist in 2003.

In the US the bug is also called a stink bug because of the sickly smell it produces.