On warm spring nights in Australia, a tiny traveller begins an incredible journey. The Bogong moth, long overlooked, is now rewriting what we know about insect migration.
In a study published 19 June in Nature, scientists revealed that Bogong moths (Agrotis infusa) use constellations and the Milky Way to steer across the country. The discovery marks the first evidence of an invertebrate using the stars to guide long-distance travel.
Celestial Maps and Magnetic Senses
Researchers from Lund University, Australian National University and UniSA studied how the moths navigate to the alpine caves of the Snowy Mountains. They found the nocturnal flyers rely on a stellar compass and Earth's magnetic field.
Each year, around four million moths migrate up to 1,000 kilometres to hibernate in the cool dark of mountain caves. In autumn, they make the return trip to breed and die, continuing the cycle.
Using flight simulators in magnetically neutral labs, scientists exposed moths to different sky conditions. When shown a natural starry sky, they flew in the right seasonal direction. When the stars were rotated 180 degrees, the moths reversed course. But if the stars were scrambled, the insects lost their way.
Even when skies were cloudy, the moths held course by switching to Earth's magnetic field. This two-part system helps them stay on track no matter the weather.
Complex Brains in Tiny Bodies
Scientists also recorded brain activity and identified specialised neurones tied to sky orientation. These brain cells lit up most when the moths faced south, confirming how precise their internal compass really is.
"This shows a tiny insect brain can handle big tasks," said lead author Prof Eric Warrant of Lund University. "These moths aren't just drawn to light. They're reading the sky."
Co-author Prof Javaan Chahl from UniSA added that similar discoveries helped design sensors for robotic navigation in the dark. His earlier work on dung beetles inspired new AI systems that copy how insects read the Milky Way.
Saving the Skies for Future Migrations
Bogong moth numbers have dropped sharply in recent years, leading to their "vulnerable" status. Scientists now stress the need to preserve dark skies and mountain habitats along their path.
“This isn’t just about moths,” said Warrant. “It’s about how life, both large and small, uses the world above to find its way.”
The study not only highlights the intelligence of insect navigation but also points to future uses in technology and conservation. It reminds us that even the quiet flutter of a moth’s wings can carry a message written in the stars.
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