Atlas moth

The Atlas moth (Attacus atlas) is a large saturniid moth found in the tropical and subtropical forests of Southeast Asia, and is common across the Malay archipelago to Indonesia. In India, Atlas moths are cultivated for their silk in a non-commercial capacity; unlike that produced by the related Silkworm moth (Bombyx mori), Atlas moth silk is secreted as broken strands. This brown, wool-like silk is thought to have greater durability and is known as “fagara.” Atlas moth cocoons have been employed as purses in Taiwan.

Atlas moths are considered to be the largest moths in the world in terms of total wing surface area (upwards of c. 400 square cm or 65 square inches). Their wingspans are also amongst the largest, from 25-30 cm (10-12 inches). Females are appreciably larger and heavier. (The largest lepidopteran in terms of wingspan is thought to be the owlet moth Thysania agrippina.) Atlas moths are said to be named after either the Titan of Greek mythology, or their map-like wing patterns.

Atlas moths are predominantly tawny to maroon in color with roughly triangular, diaphanous “eyes” on both forewing and hind-wing, bordered in black. The purpose of these dramatic, gossamer portals is not clear, but they are thought to play a role in predator avoidance. Their bodies are hairy and disproportionately small compared to their wings. Patterns and coloration vary among the many described subspecies. Male Atlas moths are distinguished from females by their smaller size, more tapered wings, and larger, bushier antennae. Neither sex possesses fully-formed mouthparts and therefore do not feed; they survive entirely on larval fat reserves throughout their 1-2 week adult life.

Females are sexually passive, releasing powerful pheromones which males detect and home in on with the help of chemoreceptors located on their aggrandized, feathery antennae. Males may thus be wooed from several kilometers downwind. Atlas moths are unsteady fliers and the female barely strays from the location of her discarded chrysalis: she seeks a perch where the air currents will best carry her pheromones.

Following a short romance, the female lays a number of spherical eggs 2.5 mm in diameter on the undersides of leaves. Dusty-green caterpillars hatch after about two weeks and begin to tirelessly feed on the foliage of certain citrus and other evergreen trees. The caterpillars are adorned with fleshy spines along their backs which are covered in a waxy white substance. After reaching a length of about 4.5 inches (115 mm), the caterpillars pupate within papery chrysalides redolent of desiccated leaves. The adult moths emerge after about four weeks.

Interestingly, Atlas moths are also capable of parthenogenesis: any unfertilized eggs laid by a female will develop into males.

The Atlas moth was first discovered in the Sanjay Gandhi National Park, Mumbai, India.

PHOTO CAPTION: Photograph of a female Atlas moth (Attacus atlas) by Gregory Phillips