By: Mary Duffy
I am sure this is a question that popped into primitive man’s head when he first discovered the pleasures of a campfire. And even as enlightened as modern man is, he still doesn’t have a definitive answer. First, not all moths are attracted to light, and researchers do not agree why some are and some aren’t. The most acknowledged theory is that over millennia, moths evolved to use celestial objects to navigate at night—the moon being the dominant glowing orb.
Unfortunately, moths might find a bright light bulb more compelling than the moon, and when they get near the source, they can’t navigate properly and end up flying in circles. After “hitting” the moon—an accomplishment they never evolved to cope with in nature—they spiral round and round until frying themselves or escaping to the dark and nature’s light. The use of celestial objects for navigation also explains why fewer moths appear to flock to artificial lights on well-moonlit nights.
Other sources disagree with the moon hypothesis and note that some moths actually veer away from the light at the last minute. To the moths—who have compound eyes that are sensitive to ultraviolet but not good at focusing—the area just outside of the light appears dark. Because they are nocturnal, the moths head toward the dark, then back to the light in a confused, erratic pattern.
It appears that this navigational accident could be detrimental to a species that finds lights irresistible, because predators—such as bats, birds and spiders—often make a feeding frenzy of the melee. This also explains why light fixtures fill with the wings and powdery remains of moths who’ve flown—like Icarus to the sun—too close to the moon.