Guided by the stars and the glow of the Milky Way, these nocturnal insects embark on their annual spring migration to a few select caves in the Australian Alps, where they seek refuge from the summer heat.
Just months later, in autumn, they make the return journey to breed, after which they die.
New research published in the journal Nature on Thursday is shedding light on one of nature's great migratory mysteries, involving the incredible journey of four billion moths each year.
Professor Eric Warrant, who researches nocturnal vision in insects at Sweden's Lund University, said while it is known that some birds and even humans use stars to find their way over long distances, this was the first time it had been proven that an insect can do it too.
"Bogong moths are incredibly precise," he said.
"They use the stars as a compass to guide them over vast distances, adjusting their bearing based on the season and time of night."
Scientists made the discovery after using special flight simulators to record moth brain activity in controlled environments.
They tested how moths find their way under different sky conditions.
When the moths saw a normal starry sky and there was no magnetic field, they flew in the direction of the season, south in spring and north in autumn.
When the starry sky was flipped upside down, the moths changed direction to match.
But when the stars were scrambled, the moths appeared to get confused and failed to fly in any specific direction.
"This proves they are not just flying towards the brightest light or following a simple visual cue," Prof Warrant said.
"They're reading specific patterns in the night sky to determine a geographic direction, just like migratory birds do."
The Australian Bogong moth, which can fit in the palm of a hand, has seen a sharp decrease in population over the past years, with the insect deemed vulnerable.
The insects are often found in Australia's south, and were once a source of food for First Nations people.
Researchers said the study highlighted the importance of protecting migratory pathways and the dark skies that the moths rely on.
"This is not just about a moth, it's about how animals read the world around them," Prof Warrant said.
"The night sky has guided human explorers for millennia. Now we know that it guides moths, too."
