In the summer, the walls of the caves in the Australian Alps are tiled with Bogong moths.

Months before, billions of these small, nocturnal insects migrate about 600 miles to this destination — a place they have never visited before. Seeking refuge from the summer heat, they travel across southeast Australia to these cool alpine caves. Then, in the fall, they migrate back to their breeding grounds, where they eventually die.

This remarkable journey has long puzzled scientists like Eric Warrant, a neurobiologist at Lund University in Sweden. “How on earth do these moths know where to go?” he said.

Now, a study in the journal Nature by Dr. Warrant and his colleagues reveals the details of the insect’s impressive feat, showing that the Bogong moth may be the first invertebrate to use the starry night sky for migration. The findings suggest the insects use a set of internal compasses, one guided by the Earth’s magnetic field and the other by the night sky, to reach their destination.

“That an insect brain that is smaller than a grain of rice is able to do this is just remarkable,” said Basil el Jundi, a neuroscientist at the University of Oldenburg in Germany who was not involved in the study.