Butterflies use magnetic compass to fly across America

http://www.bbc.com/news/science-environment-27909303

The monarch butterfly uses a magnetic compass to guide its extraordinary migration thousands of km across North America, scientists say.

Monarchs are known to possess a Sun compass but even on cloudy days they still keep flying south towards Mexico.

In a laboratory experiment, butterflies changed direction when the magnetic field around them was altered.

It suggests that like turtles and birds the insects have a geomagnetic compass, says a study in Nature Communications.

It raises concerns the butterflies may be disturbed by human-induced magnetic "noise" - which can apparently disrupt the European robin, a migratory bird.
Miracle migration

The North American monarch butterfly Danaus plexippus is famous for its epic journey from Canada to Mexico.

Every Autumn, despite never having flown more than a few hundred metres, millions of the insects set off across Lake Erie and head south for the warmer forests of the Michoacan mountains.

There they spend the winter - coating the trees in an amazing display which attracts thousands of tourists.

The ancient Mayans believed the butterflies were the souls of the dead, and the insect has become a symbol of North American trade and cooperation.