As evening sets in, adult female luna moths deposit eggs, singly or in clusters, on the tops and bottoms of the leaves of a host plant. The eggs, smaller than the head of a pin, are white and faintly oval-shaped, coated in a brown adhesive to help them cling to the host plant. Of the most common host plants—hickory, walnut, sweet-gum, persimmon, sumac, and birch—moths at MLBS most likely utilize hickory and birch. After 7-10 days, the tiny caterpillars emerge from their eggs, able to sit at fullest extension upon the eraser of a pencil. However, in only three or four weeks, the caterpillars shed their skin five times, doubling their length about every week until they are 70 mm (2¾ in) long. When the solitary caterpillars have matured to their fifth instar (moult), they begin to wander from their original host plant. When they find a suitable tree, they wrap themselves in leaves and spin cocoons. If winter is approaching and the leaves fall before the moth has emerged, the pupae will overwinter hidden in the leaf litter.
When the young moths are mature, they emerge from their cocoons in the morning, allowing their wings time to dry before the night. Like most moths, they are strictly nocturnal. The males, emerging first, disperse over great distances. As soon as the females emerge, they begin releasing pheromones to attract the males, and will generally mate with the first male they encounter. After mating, females begin to lay eggs on suitable host plants, and continue doing so until their death one or two nights later. These moths, surviving at the most for a week, never eat.
The adult male luna moths are easily distinguished from the females by their “bushier” antennae. These serve to help the moth locate and pursue females by detecting pheromones. Despite the subtle, leaf-like coloration of these moths, they are common prey for many animals, both vertebrate and invertebrate. The caterpillars, however, have several defense mechanisms against predation. If threatened, they will rear up into a defensive position and click their mandibles before regurgitating a foul-tasting substance that deters predators.
Luna moths are found in most deciduous forests of eastern North America, as far north as Canada and as far south as northern Mexico. They occur in several distinct broods (generations) each year. However, they are threatened, especially in urban areas, by habitat destruction and by the use of bright lights which distract mating. MLBS is fortunate to be located in a prime luna moth habitat, and despite their short-lived nature, a brood has recently emerged and they have been a common sight on the sides of buildings or lights in the daytime. I could not collect a live moth as there were none to be found this morning, and containing an adult overnight would badly disrupt its short lifespan. This specimen courtesy of Butch Brodie.