One morning last week good fortune smiled on me in the form of a handsome male Luna moth. While visiting a day care center, a teacher directed my attention to a gorgeous moth that had crashed on the sidewalk just outside the entry to the center. While many of the insects visited in Bug of the Week are found in more natural settings, it is not unusual to find large silk moths like Royal Walnut moths, Polyphemus moths, or Luna moths either on or near man-made structures such as schools, churches, or warehouses. Most moths take flight at night in search of mates, food, or places to lay eggs. As the old adage says, “attracted like moths to a flame” - Luna moths and their silk moth cousins are regularly lured to the bright security lights illuminating buildings. These nocturnal peregrinations often place them in highly visible locations on the side of a building or the ground nearby in the morning where they are easily spotted by hungry birds or trampled by unsympathetic feet.
Why are moths and other insects attracted to lights? Some scientists believe that night flying insects use light sources from distant stars and the moon to orient their flight. When light from these sources arrives at earth their light beams are parallel. By flying at a fixed angle to these beams, nocturnal insects maintain a straight course. However, beams of light from a nearby security light, campfire, or flashlight are still diverging from their source. When insects encounter these light beams, they constantly correct their angle of flight which causes them to spiral ever-inward to the source. Several other theories have been advanced to help explain the not yet fully understood reason why moths are attracted to light.
Luna moths range from Mexico to southern Canada where persimmon, sweet gum, hickory, walnut, birch, and sumac are some of the favored foods for Luna moth caterpillars. In northern portions of their range there is but one generation each year, but in the south two or even three broods may occur each year. After completing development as larvae, fully grown caterpillars move to the ground to spin a silken cocoon bedecked with fallen leaves. After surviving the winter and completing development, Luna moths emerge just in time to mate and lay eggs on tender, nutritious young leaves that will serve as the food for their young.
What became of my male Luna moth? After entertaining several youngsters and posing for photographs and videos for the insect paparazzi, the Luna was taken to a secluded woodlot full of hickory and set free on the base of a tree. Far from distracting security lights, on a warm spring night last week, I hope this magnificent creature took flight and fulfilled his biological imperative with the moth of his dreams.
Uh oh, Luna moth down! Attracted by security lights at night, this handsome moth wound up on the sidewalk by morning. Will careless feet be its demise or hordes of hungry ants dismember it? Nah, giant fingers first rescue the moth, and then it’s off to a photoshoot before being released in the forest far away from bright lights.
Bug of the Week thanks Dr. Shrewsbury for photographs used in this episode and Eloise, Abigail, and Jove for entertaining the Luna moth. The interesting article, “Effects of artificial night lighting on moths” by Kenneth Frank, and the fact-filled “Butterflies and Moths of North America” website were used as references for this episode.