Moth to a flame:
do moths really
love fire?

The full narration of the video.

Moths don't fly into flames because they love fire. On a summer night, switch on a lamp and the moths arrive, looping round and round it, bumping in and never leaving. It looks like true love. But if it really loved light, why not fly straight at it instead of circling?

Books written over a thousand years ago already describe moths rushing into fire. People have been guessing why ever since. One guess: moths mistake the lamp for the Moon and use it to find their way. Another: they're trying to escape toward the light.

But neither idea explains why they go in circles. Then scientists used high-speed cameras to film every move a moth makes near a light. The result was a surprise: moths hardly ever fly toward the light. They keep doing one thing: turning their backs to it.

Picture a blackout at home: you feel your way through the dark, left hand always on the wall. If the wall is straight, you walk a straight line. But if your hand finds a pillar, you'll walk round and round it, forever.

A moth follows just one rule too: keep your back to the brightest thing. For hundreds of millions of years, the brightest thing at night was the sky. Back to the sky, belly to the ground, and it flies level without flipping. But switch on a lamp, and the brightest thing is right beside it. The moth still turns its back to it, tilts, and ends up circling the lamp.

If the lamp is behind it, it leans back, climbs higher and higher, runs out of speed, and drops. Flying right over a lamp is worse. Now the brightest thing is under its belly, so it flips over and dives into the ground. This rule is called the dorsal light response. Dragonflies, beetles and many other flying insects have it.

Under a streetlight on a summer night, all that circling, climbing and dropping, and flipping, is this rule at work. The wall is the sky, and the pillar is the lamp. They also tried an experiment. They pointed a lamp up at a big white sheet overhead, like a patch of sky. Moths flew happily beneath it, without crowding the lamp. Point the lamp down at a white sheet on the ground, and the moths flip over, one by one, and crash.

Scientists suspect lamps don't call moths in from far away; they just trap the ones flying past. Fire works the same way. The moth circles the flame closer and closer, until a wing touches it and burns. So moths don't fly into flames out of love. It's an ancient rule that has kept them flying for hundreds of millions of years, meeting something new.

Streetlights with shades that shine only downward trap fewer insects. Tonight, watch a streetlight for one minute. Do the moths crash straight into it, or circle around it? Come back and tell us.