Why Do Moths Fly Into Lights?

Step 1 of 5

The old rule is: keep the light to one side.

For millions of years the only bright things at night were the moon and stars. Holding one at a steady angle over your shoulder is a simple, reliable way to fly in a straight line.

Step 2 of 5

A nearby light breaks it.

The moon is so far away the angle barely shifts however far you fly. A lamp two metres away shifts constantly, so holding the angle steady curves the moth in tighter and tighter.

Step 3 of 5

It is a moon-lit animal in a lit-up world.

Moths evolved when nights were dark. Streetlights, porch lights and windows are all new, and each one is a small trap that never lets the moth go on with its evening.

Step 4 of 5

A moth smells better than almost anything alive.

A male moth's feathery antennae can pick up a few molecules of scent from a female more than a kilometre away, and fly upwind along the trail until he arrives.

Step 5 of 5

Moths and butterflies are close cousins.

Most moths fly at night, rest with wings flat, and have feathery antennae. Most butterflies fly by day, rest with wings up, and have thin antennae with a knob. There are exceptions to all of it.

Warm-white lights and shielded lamps that point down catch far fewer moths than bright, bare, blue-white ones.