Invertebrates
Atlas Moth
Attacus atlas · also called snake's head moth
The atlas moth is a giant with a short, single purpose. It spends months as a fat green caterpillar, then emerges as one of the largest winged insects on Earth — and, with no mouth and no way to eat, it has about a week to find a mate before it dies.
Overview
Atlas moths live in the forests and scrub of South and Southeast Asia, from India and Sri Lanka through southern China to Indonesia and the Philippines. They are members of the giant silk moth family (Saturniidae), and like their relatives the adults are nocturnal, non-feeding, and short-lived. The caterpillars are the feeding, growing stage, and they are host-plant generalists, eating the leaves of citrus, cinnamon, guava, and many other trees and shrubs.
The largest wings
An atlas moth’s wingspan can reach 30 centimetres, and its total wing area is among the greatest of any lepidopteran. The wings are a rich reddish-brown with triangular transparent “windows” near the centre and a bold pattern of white, pink, and black bands. The forewing tips are elongated and marked to look like the head of a snake — the origin of the name “snake’s head moth” and, possibly, a deterrent to predators.
An adult that cannot eat
The adult atlas moth has no functional mouthparts and a shrunken digestive system. It cannot take in food or, effectively, water, and lives entirely on energy stored during the caterpillar stage. That gives it roughly five to seven days of life, all directed at reproduction. It flies weakly and mostly at night, and it stays still and camouflaged by day.
Finding a mate
Because the adults do not feed and do not live long, mate-finding has to be fast and reliable. A newly emerged female stays put and releases a species-specific pheromone. Males, equipped with enormous feathery antennae that can detect a few molecules of that scent, fly upwind to find her — sometimes from more than a kilometre away. After mating, the female lays her eggs on a suitable host plant and dies.
Atlas moths and people
The species is Least Concern, widespread, and common in appropriate habitat, and it adapts to gardens and plantations. It is kept and bred by hobbyists and butterfly houses worldwide, and its cocoons are used on a small scale to make fagara silk, a coarse brown fabric, in parts of India. Localised threats are the usual ones for forest insects — habitat clearance and pesticide use — but there is no evidence of broad decline.
Atlas Moth: common questions
How big is an atlas moth?
Its wingspan reaches 24 to 30 centimetres — about the size of a dinner plate — and its total wing surface area is among the largest of any moth or butterfly, rivalled only by a few other giant silk moths and the white witch moth. Females are larger and heavier than males, with broader wings. The body is surprisingly small and furry compared with the enormous wings.
Is it true the atlas moth never eats?
Yes. The adult atlas moth emerges from its cocoon with no functional mouth and a reduced or absent gut. It cannot feed, and it survives for only about a week on the fat reserves it built up as a caterpillar. Everything about the adult stage is devoted to reproduction — the female releases pheromones and waits, the male flies to find her, they mate, she lays her eggs, and both die within days.
Why do the wings look like snakes?
The tip of each forewing is drawn out into a triangular point with markings — a curved dark band, an "eye" spot, and a tapering shape — that together resemble the head and hood of a cobra viewed side-on. When the moth is disturbed it may drop to the ground and slowly flap the wings so the "snake heads" writhe. Whether this genuinely scares off birds and lizards is debated, but the resemblance is striking and the pattern is called the "snake's head" for that reason.
Can you get silk from an atlas moth?
A little. The atlas moth spins its cocoon from a brown, broken silk called fagara, and in parts of India (notably among some communities in the northeast) the cocoons are collected and the silk spun into a durable, wool-like brown cloth. Because atlas moth silk comes in short lengths and the moth cuts its way out of the cocoon (unlike the domestic silkworm, which is killed inside its intact cocoon), it cannot be reeled and is only used on a small, traditional scale.