Column: The magnificent Luna Moth
Published 12:52 am Monday, March 27, 2006
A few nights ago, I saw the first moths of the year. They were just little, nondescript brown jobs but as I watched them going bonkers around the yard light thoughts of the magnificent luna moth came to mind.
The luna silkmoth, as its truly named, is so un-moth like one would think it to be a giant, brilliant butterfly of the tropics. Spanning over four inches, their pale, pastel green wings with long tails flowing gracefully behind like fluttering ribbons are truly stunning. Anyone that has personally met a luna moth is held in awe. I haven't seen a luna moth in decades and I wondered what's going on with them. Are they quietly slipping unnoticed into oblivion like too often happens?
In nosing around a bit it appears my lack of sightings is mostly a matter of bad luck for their populations are reported stable throughout their range. One reason for the void is the time I spent in the Pacific Northwest. The luna moth only inhabits the Eastern portion of the country. It ranges from the Canadian seashores of Nova Scotia west to Saskatchewan and south to Texas, the Gulf Coast and Florida.
The luna moth's habitat is deciduous forests where the larvae, or caterpillar as we prefer to call them, dine on a variety of tree leaves, the most preferred being white birch, the various hickories, walnut, and some sumac species. Further south persimmon and sweet gum are favorites.
The life cycle of the luna moth is similar to many butterfly and moth species. Anywhere from one to a half dozen eggs are laid on the leaf of a larvae host plant, usually on the underside. The eggs are fairly large, dark, grayish-brown cylinders with a concave upper side. In approximately a week, the eggs hatch and a relatively small larvae begins its journey in life. Over the next several weeks the larvae grows rapidly.
Four times it will outgrow its skin, each time shedding the skin like a snake. The stage between each shedding is called an instar. The caterpillar is bright green with faint yellow stripes down the sides. At its largest it will be around three inches long, give or take a little, and thick and robust. Here in the north country the luna moth only goes through one life cycle per year. As summer wanes the caterpillar will crawl down from its host plant to the leaf litter underneath and spin a cocoon, or chrysalis as the technical types call it, using silk made by the caterpillar to bind leaf debris. There, snuggled in its shell under the loose leaves on the ground the luna will while away the winter.
The following year, sometime between May and July, the adult begins to stir inside the chrysalis. It secrets a concoction called cocoonase to break down the silk binder. Using horn like projections near the base of its forewing it begins to tear away at the weakened silk chrysalis. Once out the adult moth climbs upward and spreads its wings to dry. The sole purpose of the adult luna moth is to reproduce. It has no developed mouth so cannot eat or drink. It will only a live a week, hopefully just long enough.
In the late evening, the female extends a scent gland from her lower abdomen and wafts her pheromones onto the night breeze. She has not yet experienced flight but somewhere out there in the dark of night her future suitor is on winged patrol, seeking the siren scent of her magic potion. After mating she takes wing for the first time to find appropriate host plants that will nourish her larvae. Once her two hundred or so eggs have been dispersed throughout the forest her job in life is done and soon over.
Unfortunately, since luna moths don't eat there's not much we can do to attract them to our property other than planting the aforementioned larvae host trees. Another thing that helps is to not rake the leaves underneath the host trees for that is where the chrysalis overwinters. Other than that, about all you can do is hope. Carpe diem.