The skull moth is a moth that lays its eggs in Europe in the summer and then migrates to Africa where it overwinters.

It is easy to recognize because it has a skull-like mark on its back, which has made it a mythical insect.

The man-in-law became famous through the 90s film "When the lamb falls silent" and it spreads its yellow wings on the film poster itself.

Radio transmitter on the back

Now the skull-warmer is the first nocturnal insect that biologists have successfully tracked to map its migration routes.

Biologists at Germany's Max Planck Institute for Animal Behavior glued small radio transmitters to the butterflies' backs.

They released them in southern Germany and were able to follow the journey south from a small single-engine aircraft.

- We flew with them and were able to track them individually as they flew over the Alps.

We followed a swarmer for ninety kilometers.

When it gets light in the morning, they land and sit on a tree trunk to sleep, says Myles Menz who is a zoologist at the Max Planck Institute and who led the experiment.

The study was published in this week's Science.

Straight direction south

The experiment showed that the skull swarms flew in unexpectedly straight paths, which according to Myles Menz is unusual for animals that fly long distances.

When the wind was strong, they flew closer to the ground to better control the gusts.

Then they can also compensate for the wind direction.

If there is, for example, a strong side wind, they steer against the wind so as not to drift in the wrong direction.

In this way they keep their straight direction south.  

"This ability suggests that the skull swarms have a sophisticated magnetic compass that allows them to navigate so well," says Myles Menz.

Still great mystery

Many studies have been done on migratory birds and migrating insects, but they have not yet figured out how this magnetic compass works.

- Finding out where the magnetic mind is located on these animals is still one of the big challenges for us, says Myles Menz.

Play the video to see Myles Menz working the skull warmers.