Why do moths fly around street lamps at night?
Let’s celebrate moths during National Moth Week. We’re not talking pesky pantry moths, but rather those exquisite nocturnal critters that fly around our porch lights.
Why do moths fly around streetlamps and other artificial nighttime lights?
The question has puzzled people since the invention of electric lights. The gaslights in early use weren’t nearly as bright as the new electric lights, which suddenly lured moths.
Scientists used to think that bright, outdoor electric lights mimicked the moon and stars, which moths use to orient themselves. Since moths were here when nighttime light came only from the heavens, their confusion over nighttime electric lights seemed plausible.
After all, migratory moths have been navigating by celestial lights for eons. Using transverse navigation, migratory moths orient themselves by maintaining a steady angle to the moon and stars.
Perhaps those moths navigating by celestial lights also orient themselves via streetlights. The only problem is that more than 70 percent of moths don’t migrate — and therefore don’t need lights for navigation.
They simply meander aimlessly around porch lights and streetlights.
Another theory involves dorsal light reaction, which inclines moths to keep lights above them as they’ve done with the moon and stars from time immemorial. The theory posits that moths are compelled to angle their flight downward toward artificial lights as though keeping celestial lights above them.
But because most nocturnal moths don’t need celestial lights to find their way, what attracts them to artificial lights? And what explains nocturnal moths that aren’t drawn to artificial lights?
The mystery remains unsolved.
So let’s enjoy the pretty moths hanging around the porch light. Maybe we’ll see one land against a vertical wall, with its decorative wings spread out.
Among the most alluring species are the silkworm moths, named for spinning sticky silk to form a cocoon where a worm transforms into a moth.
One example is the Luna moth, named for the Roman moon goddess. It has pastel green wings with a 3- to 4-inch wingspan and two 3-inch-long streaming tails. The tails twist in flight, disrupting sound waves and, thereby, disorienting predatory bats.
The Io moth gets its name from the mythological Greek priestess to the wife of Zeus. It has yellow or tawny wings with large twin ovals that mimic owl eyes, which help to frighten predatory birds.