Atlas Moth (Attacus atlas): One of the Largest Moths on Earth

What does an Atlas moth look like?

An Atlas moth is mostly warm reddish brown, with wavy bands of black, white, pink and purple across all four wings. Each wing has a large triangular “window”, a patch without scales that looks almost transparent and is edged in black. The undersides are paler.

The most striking feature is the tip of each forewing. It is extended and curved, with a dark spot, a yellowish edge and markings that look strikingly like the head of a snake, complete with an “eye” and “mouth”. In Cantonese the moth’s name means “snake’s head moth”. You can read about this disguise in why Atlas moth wings look like snake heads.

The body is small and furry compared with the huge wings. Males have broad, feathery antennae used to detect females, while females have narrower antennae and a larger, heavier abdomen full of eggs.

How big is an Atlas moth?

Atlas moths usually have a wingspan of about 24–28 cm (9.5–11 in). Females are larger than males. A wingspan of about 30 cm (12 in) has been claimed for exceptional specimens, but such records are not well verified.

Whether it is “the largest moth” depends on the measure. The white witch moth of Central and South America has a wider wingspan, and the Hercules moth of New Guinea and northern Australia has the largest documented wing area of any insect. Published figures for the Atlas moth’s wing area vary widely between sources. See what is the largest moth in the world? for the full comparison, or the largest insects in the world.

Habitat and range

Atlas moths live in tropical and subtropical forests across South and Southeast Asia. Their range stretches from India east through southern China, Myanmar, Thailand, Laos, Cambodia and Vietnam to Malaysia and Indonesia, including Sumatra, Java and Borneo. A subspecies lives on Yonaguni Island in southern Japan.

They are found in dry and moist tropical forest, secondary forest that has regrown after clearing, forest edges and shrubland. Because their caterpillars eat many kinds of trees, they can also turn up in gardens and plantations near forest.

The name “Atlas moth” is sometimes used loosely for all members of the genus Attacus, which includes more than 20 named species and subspecies. The similar Attacus taprobanis of southern India and Sri Lanka was once treated as part of the same species.

Life cycle: eggs, caterpillars and cocoons

The life cycle has four stages: egg, caterpillar (larva), pupa and adult.

Eggs. Females lay round eggs about 2.5 mm across in small groups, usually on the undersides of leaves of food plants. The caterpillars hatch after roughly two weeks and often eat their eggshells first.

Caterpillars. Young caterpillars are pale and dusty-looking, and they become pale bluish green as they grow. Large caterpillars carry rows of fleshy, white, waxy spines along the back, and the tail end has a green spot ringed with orange. They feed on the leaves of many trees and shrubs, including citrus, cinnamon, guava and other evergreen species. Over about two months they molt several times and reach about 11.5 cm (4.5 in) long.

Cocoon. A fully grown caterpillar spins a papery cocoon of tough brownish silk, about 7–8 cm (3 in) long, often wrapped in dry leaves and hung from a twig by a silk strand. Inside, it changes into a pupa.

Adult. After about four weeks, depending on temperature, the adult moth emerges, pumps fluid into its crumpled wings and waits for them to dry and harden.

Why adult Atlas moths never eat, and how they find a mate

Adult Atlas moths have only tiny, non-working mouthparts and never feed. They live entirely on the fat stored by the caterpillar. Because every flight burns precious energy, they spend most of their short adult life resting, usually becoming active at dusk and night.

Adults live only about one to two weeks. Their only task is to reproduce. The same is true of many other giant silk moths, including the North American luna moth.

A newly emerged female usually stays near her cocoon and releases a scent, called a sex pheromone, from a gland at the tip of her abdomen. Males detect this chemical with their large, feathery antennae, which carry many sensory hairs, and fly upwind to find her. Males of giant silk moths are famous for finding females over long distances, reportedly several kilometers.

After mating, the female lays her eggs on suitable plants over the following days and then dies. Adults can be seen at any time of year in the tropics, although they are more common in some seasons.

Predators and defenses

Atlas moths are eaten by birds, lizards and other predators, and their caterpillars are attacked by birds and parasitic wasps and flies.

Adults rely on bluff. When disturbed, an Atlas moth may drop to the ground and slowly move its wings, making the snake-head wingtips more visible. Large, motionless moths may also benefit from simply looking too big and strange to be food. The waxy spines and large size of the caterpillars may help deter some predators as well.

How the Atlas moth compares with other giant moths

The Atlas moth belongs to the family Saturniidae, the giant silk moths, which includes many of the world’s biggest and most colorful moths. Several relatives are easily confused with it.

In the Americas, moths of the genus Rothschildia look like smaller versions of the Atlas moth, with similar clear wing windows, which is why they are sometimes mistaken for it. They are only distant relatives within the same family.

Behavior of adult Atlas moths

Adult Atlas moths are weak, slow fliers. Their wings are large but the body and flight muscles are small, so they flap slowly and avoid long flights. During the day they hang quietly on tree trunks, branches or leaves, often with the wings spread flat, which shows off the wing pattern and the snake-head tips.

Most activity happens in the evening and at night. Males do most of the flying, searching for the scent of a female. Females usually fly only after mating, to find plants on which to lay their eggs. Because adults cannot refuel, a moth that is disturbed and forced to fly repeatedly may use up its energy and die sooner.

Myths and facts about Atlas moths

“Atlas moths are the biggest insects in the world.” Not quite. They are among the largest by wingspan and wing area, but the white witch moth has a wider recorded wingspan, the Hercules moth has a bigger wing area, and heavy beetles, giant wētā and stick insects beat them in weight or body length.

“Atlas moths have no mouths.” Adults do have mouthparts, but they are tiny and do not work, so the moths cannot eat or drink. In practice the result is the same: adults live on stored fat.

“Atlas moths are poisonous.” There is no evidence that adults are toxic to people. They are harmless to handle in butterfly houses, although their delicate wing scales are easily damaged, so visitors are asked not to touch them.

Atlas moths and people: silk and butterfly houses

The Atlas moth is one of the so-called wild silk moths. In parts of India its cocoons are gathered on a small scale for a brown, wool-like silk known as fagara. Because the caterpillar spins broken strands, this silk cannot be reeled into long threads like that of the domesticated silkworm, but it can be spun into yarn and is said to be strong and durable. In Taiwan, empty cocoons have been used as small purses.

Today Atlas moths are best known to people in Europe and North America from butterfly houses and zoos, where visitors can see the huge adults resting on walls and plants.

Conservation status

The Atlas moth has not been assessed on the IUCN Red List, so its official status is Not Evaluated. It remains widespread, but like other large forest moths it is affected by forest loss and fragmentation, pesticides and artificial light at night, which can draw moths away from their habitat. Learn more about that problem in why moths are attracted to light.