Luna Moth Facts

A mature luna moth spans 8 to 11 centimeters and weighs 1 to 2 grams. Its translucent green wings have a leading edge that is maroon in southern populations and purplish-brown in northern ones. The semi-transparent eyespots can startle predators. Males have feathery (plumose) antennae with thousands of sensors tuned to female pheromones, while females have narrower antennae and a fuller abdomen. The long, twisted hindwing tails spin in flight and interfere with the ultrasonic echolocation of hunting bats, directing some attacks toward the expendable tail rather than the body. The species belongs to the giant silkmoth family Saturniidae; its caterpillars feed for several weeks, while adults do not feed.

The luna moth is endemic to North America, from the boreal forests of Nova Scotia and Saskatchewan south through the eastern United States to the Gulf Coast and into northern Mexico. It lives in temperate deciduous forest, mixed woodland, and well-vegetated suburbs wherever its larval host trees grow, preferring mature, continuous canopy but tolerating fragmented woods with low light pollution. Artificial light badly disrupts its navigation and mating, drawing adults out of the canopy and leaving them spent and exposed by dawn.

Only the caterpillars feed. Adults are aphagous, emerging with vestigial mouthparts and no functional gut and using fat stored during the larval stage for flight and reproduction. Caterpillar diets vary by region: northern populations favor white birch, while southern ones use sweetgum, hickory, walnut, and sometimes sumac. A caterpillar feeds on foliage and molts through five stages (instars) over three to four weeks before pupating.

Luna moths are solitary, meeting only to mate, and strictly nocturnal. By day adults stay motionless under branches or among leaves, their green blending flawlessly into the foliage. Mating is chemical: after midnight a virgin female climbs to a high perch and "calls," extending a gland at the tip of her abdomen to release a sex pheromone downwind. A male can detect just a few molecules from over a mile off and follows the plume upwind through the canopy to reach her; copulation is prolonged, often lasting from the small hours into the next evening.

The luna moth undergoes complete metamorphosis. After mating, the female lays 200 to 400 mottled brown eggs, singly or in small clusters, on the undersides of host leaves, and they hatch in 10 to 14 days into 2-millimeter caterpillars. The larval stage lasts about a month; at its final instar the engorged caterpillar drops to the forest floor, draws a fallen leaf around itself, and spins a papery brown silk cocoon, then sheds its skin to reveal the pupa. Northern populations produce one generation a year, southern ones up to three, and the season's last pupae overwinter in diapause, emerging the next spring. The adult then lives just 7 to 10 days.

The luna moth is Least Concern, generally stable across its wide range, but faces real local pressures. Habitat loss and the fragmentation of mature deciduous forest reduce regional abundance, and light pollution is an increasingly serious threat — bright streetlights and commercial lighting scramble the moths' moon-based navigation, sending them spiraling around artificial lights until they die of exhaustion or are eaten. The parasitic tachinid fly Compsilura concinnata, introduced to control the invasive spongy moth, also kills many native silkmoth caterpillars, luna moths among them.

• University of Florida Entomology and Nematology: Luna Moth (Actias luna)
• U.S. Forest Service: Luna Moth Species Profile
• Butterflies and Moths of North America (BAMONA): Actias luna Data