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The Giant Silk Moth-An Entomological Fairy Tale

© Renie Burghardt

The other day at sunset, I saw my first Luna moth of the spring-a pale green, shimmering apparition fluttering against the boards of the house on velvet wings. The luna moth, with its silky, plush wings, furry body, and delicate long legs, is a lovely, ethereal vision to behold on a spring evening.

The life story of every giant silk moth is an entomological fairy tale of sorts, because from the soft and repulsive body of the caterpillar, full of the juice of walnut leaves, (as in the case of the Luna moth larva) comes the lovely presence of the adult. For in the cocoon, the tissue of the caterpillar break down and evolve to a higher plane. Suddenly, the humble and repulsive larva takes on beauty and grace, as it emerges with fluttering wings on its mission to mate and propagate the next generation.

The largest members of the Order Lepidoptera, which includes all butterflies and moths, giant silk moths, are of the family of Saturniids, a group of some 1500 giant sized moths. Most of these giant sized moths live in the tropics, the largest one being the Hercules moth of Australia, which has a wingspan of 12 inches. In North America the Luna, Polyphemus, Cecropia, Ceanothus, Io, Promethea, Ailanthus and Imperial silk moths are among the biggest.

Because the beautiful adult stage of the giant silk moth is so brief, lasting only about a week, most people never see them. Most of them usually fly at night, the females emitting pheromones to attract males. Males can smell the pheromones miles away with the help of their sensitive receptors at the tips of their antennae. So they often fly great distances to reach females, and remain together for a day or so while they mate.

Females begin searching for shrubs and trees that will provide nutrition for their larvae, and lay their eggs on them the day after mating. The Cecropia moth, the largest of our giant silk moths with a wingspan of up to 7 inches, can lay more than one hundred eggs, usually on the underside of oak and hickory leaves, or other hardwoods. After laying their eggs, the females usually die, while the males may mate again, but also die soon. In their brief, winged life, the giant silk moths do not even feed, lacking a mouth; there is only enough time to carry on their life's work-procreation!

Depending on the right weather conditions, the tiny larvae hatch in about a week to two weeks. Since they are food for birds, spiders and other insects, many of them don't live long enough to take their first bite of a leaf. But the survivors among them soon develop heads and mouthparts for chewing.