Stargazing: The secret star maps of moths

ON a moonless night, when the world goes quiet and even the gum trees seem to hold their breath, something small is commuting through the darkness.

Not a drone. Not a late-night bird.

Just a moth, humble, silent, and roughly the size of your thumb flying with the confidence of a seasoned pilot.

Inside that tiny head sits one of nature’s most astonishing tricks: a built-in map of the night sky.

Every spring, billions of Bogong moths leave the plains and grasslands of southeastern Australia and head for the Australian Alps.

Their goal?

To locate a collection of cool, hidden caves where they can spend the scorching summer months.

Think of it as the insect equivalent of checking into a mountain resort.

The twist is that each new generation of moths has never seen these caves before.

Yet somehow, every year, they locate them with pinpoint accuracy.

So, how do they pull off this annual disappearing act?

To answer that, scientists built something that sounds like it belongs in a sci-fi film: a custom-made “moth planetarium.”

Inside this tiny dome, researchers gently tethered the moths so they could flap as if in free flight, then projected the night sky overhead.

When shown a real star field, the moths turned and “flew” exactly in the direction their migration requires.

But when the stars were scrambled into a random, nonsensical pattern, the moths’ sense of direction collapsed completely.

The real magic revealed itself when researchers monitored the moths’ brain activity.

Their visual neurons, the cells that process what they see, lit up most intensely when the stars matched the proper heading for their journey.

And one region of the sky stood out more than any other: the Milky Way, especially the portion near the Carina Nebula.

The moths weren’t just flying under the stars; they were navigating by them, treating the galaxy like a glowing signpost in the dark.

But nature, ever the clever engineer, didn’t stop there.

When the stars vanish behind clouds, the moths switch to a backup system: Earth’s magnetic field.

This two-part navigation kit, celestial compass plus magnetic compass, makes Bogong moths some of the most sophisticated travellers in the insect world.

They’re not entirely alone in this talent.

Migratory birds, dung beetles, and even certain species of seals are known to use the stars as navigational cues.

But few do it with the understated grace, and sheer improbability, of the Bogong moth.

It’s a humbling reminder that humans aren’t the only ones with a relationship to the night sky. Long before telescopes, space probes, or apps that tell us when to look up, insects were quietly steering their way across continents using the light of distant suns.

And here’s where the story takes a worrying turn.

As artificial light spreads across our cities, the stars grow fainter.

With them goes an ancient guidance system that countless creatures, including these tiny alpine tourists, depend on. If the night sky continues to fade, what happens to the travellers who rely on it?

So the next time a moth flutters around your porch light, spare it a moment.

You might be watching a veteran of a thousand-kilometre trek, guided not by GPS, but by the shimmering arc of the Milky Way, a fellow wanderer whose map is written across the heavens themselves.

By Dave RENEKE, Astronomer