Nobody taught them: Scientists are stunned by how these tiny insects use the Milky Way as a guide to travel 1,000 km

A small insect, the Bogong moth, travels 1,000 kilometres every year at night across Australia. These moths leave the heat of southeastern Australia in spring to rest in cool caves in the Australian Alps. They return in autumn to mate and die.

A new study shows that these moths use the stars to guide them, just like birds and humans. This is the first time such a skill has been found in insects.

The Bogong moth, now endangered, has a wingspan of about 5 cm. They sense Earth’s magnetic field, which gives them a backup if the sky is cloudy.

Scientists studied around 400 Bogong moths to understand how they travel 1,000 km at night. Now, they are amazed at how these small-brained creatures manage such complex navigation.

These moths can see dim stars 15 times brighter than humans, helping them use the Milky Way as a guide. Other animals like monarch butterflies and dung beetles also use light for navigation, but not for such long, exact journeys.

What’s truly special is that Bogong moths make this journey only once in their life and learn it by instinct. Their parents are dead before they’re born. Yet, they know where to go.

Australian researcher Eric Warrant tested if they also used stars for guidance. He set up a special lab at his home, near the moths’ destination in the Alps.

Using a light trap, he caught moths and fixed them to thin rods that allowed them to fly while recording their direction. The lab projected the southern night sky, just like it looked outside.

Amazingly, the moths flew in the correct migratory direction, south in spring and north in autumn. The experiment showed how they used star patterns to guide their way.

First for invertebrates

“It is an act of true navigation. They’re able to use the stars as a compass to find a specific geographic direction to navigate, and this is a first for invertebrates,” CNN quoted Warrant as saying.

“With a very small brain, a very small nervous system, they are able to harness two relatively complex cues and not only detect them, but also use them to work out where to go,” Warrant said.