The Luna moth
Throughout history, butterflies and moths have frequently been shown as symbols of rebirth, regeneration, and renewal – even depicted as a spiritual guide through transformation to a new self. They are the archetypal example of the soul itself, a creature with a unique gift endowed by nature to completely alter its physical form. Their ability to undergo metamorphosis and emerge as an entirely new being, from the ground-restricted caterpillar to the free-flying winged beauty is certainly a wonderful metaphor for hope and transformation.
A particularly serene and spectacular representative of Lepidoptera (the order of insects that includes moths and butterflies) is the Luna moth (Actias luna). As one of the largest moths in North America, with a wingspan that can reach 4.5 inches, Luna moths are truly distinctive, possessing a gorgeous translucent lime green color, long narrow hind wings and a set of eye spots to confuse predators. Luna moths are in the family Saturniidae, which are also known as the giant silkworm moths, for their size and the silk cocoons they make.
In all my time outside, I’ve only ever once encountered a Luna moth. This is at least partially explained by the obvious distinction itself between butterflies and moths: for the most part the former are active during the day and latter are active at night. The term Luna itself is the Latin name for the moon, and moths are even thought to use the moon for orientation. The age-old expression of someone being led as a “moth to a flame” certainly has truth to it, as moths are clearly attracted to light. This attraction is believed to be related to the moths’ use of the moon as a reference point to orient their flight patterns, and therefore they become disoriented by artificial lights. Whereas a moth is attracted to light, other creatures like cockroaches avoid it. This phenomenon of an organism moving away or toward light is known as phototaxis.
Luna moths undergo four stages of development: egg, larva, pupa and adult. The adult female Luna moths emit a pheromone to attract mates, who can sense it from up to five miles away. They then lay their eggs on a host plant. Moths feed selectively on certain species, and in some cases exclusively on a single species. Luna moths feed on a variety of deciduous trees, preferring birch, sweetgum, hickory, and walnut. A female Luna moth laying eggs will pick a tree that other silkworm moths do not, decreasing competition for the food source. After about 10-12 days, the Luna moth eggs hatch into tiny caterpillars. These larvae eat constantly for up to three weeks before weaving a cocoon. When the pupa in the cocoon mature and emerge as adults, they climb up a nearby tree to expand and harden their wings, which can take up to two hours. Adult Luna moths do not eat (they don’t even have a mouth!) and live for only a few days to one week at most, so it is rare to see one. They live only to reproduce, and the number of broods is dependent on the location and climate. In warmer climates in the south, they may produce as many as three broods, whereas in colder climates like Canada they will have only one.
The Luna moth is common in North Carolina, but populations elsewhere are decreasing, due to a combination of factors including pesticide use and habitat loss. In areas such as the Northeast they have also been negatively affected by the introduction of a parasitic wasp that was intended to help control the invasive gypsy moth. This parasite may be having a negative impact on a variety of large moths in the regions where it was introduced.
North Carolina Natural Heritage Program biologists are surveying moth populations in our area, but the information they provide is not just restricted to the species itself. Moths are an excellent indicator of the health of the whole ecosystem. As mentioned earlier, different species of moth feed upon different species of plants. In fact, all organisms in the Lepidoptera group are closely tied to the particular plants they eat, and require not only a specific type of plant but a healthy habitat comprised of those plants in order to survive. Learning more about the moths found in an area teaches us about the quality of the overall habitat, which is important information for conservation efforts on a larger scale. It is even more appropriate then that moths are a symbol for regeneration and guidance. Their presence is indicative of the health of our ecosystems, and their absence can signify the need to restore and manage for more natural conditions, to ensure that both they and other species will persist for generations to come.