It’s not just birds that fly south for the winter. Many of Europe’s skull and crossbones hawk moths also move to warmer climes in autumn. And new research shows they do so using a sophisticated navigation system comparable to that of our feathered friends.
“They don’t just get blown around,” says Myles Menz, lead author of the study published in Science. “They have a place to go and they get there.”
Menz and his colleagues were able to track the insects as they crossed the Alps by equipping them with tiny, short-range transmitters that could be tracked by scientists in a light aircraft. This showed that the moths routinely adjust their course to compensate for wind direction, allowing them to maintain a consistently straight trajectory.
They also seek the most favorable winds by varying their height. “They can get up very high to take advantage of a tailwind,” says Menz. “When there is a crosswind or a headwind, they sit low and push through.” Their exact goal is not yet entirely clear.
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“They’re probably moving to the Mediterranean, North Africa and possibly sub-Saharan Africa,” says Menz, who conducted the research at Germany’s Max Planck Institute for Animal Behavior. In this case, they may cover 4,000 km on their migratory flights. However, it’s possible that the skull and crossbones population in sub-Saharan Africa has no connection to those in Europe and stays there year-round, Menz says.
This raises the intriguing possibility that populations vary in their migration strategies – again similar to birds. There is also the question of how they know which way to go. Unlike birds, which can learn a route by following more experienced flock members and then refine their strategy over the following years, the moths, which live only a few weeks as adults, make the journey only once.
“There is really good evidence for different compass mechanisms in insects – solar compasses in day-flying insects and magnetic compasses in nocturnal moths, or navigation using landmarks. We can now try to figure out how they use these different cues to get where they want to go,” Menz says.
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Main image: the skull hawk moth (Acherontia atropos) is famous for the human skull on his rib cage. The species of moth appears in horror films The Silence of the Lambs and on the film cover. © Robin Busch/Getty
