How the migration of Australian butterflies will find caves hundreds of kilometers: NPR

Australian Bogong butterflies are not much to look at, says Anda AndreaNeurobiologist at the Francis Crick Institute. “These are small brown butterflies with arrow marks on the wings. They are quite indefinable.”

But these insects undertake an epic migration twice during their lifetime, traveling hundreds of kilometers in each direction.

Researchers have shown that the land magnetic field Help the butterflies to orient, but that alone was not enough. “They needed something visual to accompany him,” said Adden.

She wanted to know what this signal could be on such a large landscape – especially at night when there is little light.

In an article published in the journal NatureAdden and his colleagues show that the signal comes from the heavens. In other words, the starry sky allows Bogong butterflies to orient and navigate.

“This is the first time that we have found an invertebrate using the stars to navigate,” explains Adden. “And also the first time that anyone has seen neurons that specifically react to starry sky in the brain of insects.”

A winged migration of 600 miles

Bogong butterflies follow an annual pace.

They hatch in their breeding grounds in the spring of southeast Australia where it is really hot in summer. “So, if they reproduced immediately, their larvae died of hunger because there is not enough food,” explains Adden.

Instead, butterflies migrate over several nights at more than 600 miles in the south to the Australian Alps where they settled in cooler caves, entering a dormant phase called summer (like hibernation but in summer), in the millions.

“It’s just the butterfly butterfly on mites,” explains Adden. “You no longer see a cave wall. It’s just butterflies.”

In the fall, they return to their breeding grounds, mate, lay their eggs and die.

“Then, the following year, the new hatch,” said Adden. “And they never went to the mountains. They don’t have parents who can tell them how to get there.”

And yet they do it.

She suspects that the stars could just offer the signal they need. “The Milky Way is an amazing spectacle,” she says. “And it seemed to be an obvious thing to use if you are a butterfly living in this environment.”

A miniature planetarium show

To test his theory, Adden, who did his doctorate. At the University of Lund in Sweden at the time, and his colleagues caught butterflies in the Australian Alps and crossed them through one of the two experiences in the middle of the night.

The first was a behavioral test. It was a question of placing a butterfly inside what was essentially a mini-planetarium which contained a projection of the night sky and no magnetic field.

“It’s not an experience that still works,” says Adden. “We depend on the night butterflies in cooperation with us.” Fortunately, enough night butterflies have cooperated. And the result surprised the researchers.

“They did not content themselves with a circle and to make twists and turns, but they actually chose a fairly stable direction,” she said. “Not only was their migratory direction.”

In other words, butterflies used the starry sky as a benchmark originally And navigate.

The following question of Adden involved what was going on in the butterfly brain. It recorded the electrical activity of individual neurons while turning a projection of the Milky Way.

When she looked in the brain regions that process visual information, the majority of neurons were active when the butterfly faced south. This specific direction suggests that the brains of the butterflies code for management by treating the visual indices of the Milky Way.

Beyond the butterfly

Biologist Pauline Fleischmann at the University of Oldenburg studies navigation in Désert ants in Greece and says that it is fascinated by the study.

“This shows that insects, their world is probably much more filled with information than humans usually assume,” she said.

In addition, the capacity of butterflies to use visual and magnetic information to navigate can be essential for survival – in case it is cloudy, for example, or the magnetic field is not reliable. “If we fail, they have a backup system,” said Fleischmann.

Bogong butterflies are threatened. Adden says that his conclusions could help keep these insects – and everything that matters to them for food. In a first step, the reduction in light pollution would help these butterflies to continue their trip led by stars through the Australian bush.

“The protection of Bogong butterflies would help us protect the entire alpine ecosystem,” she says.