Magnetic compass helps butterflies navigate

BBC : It has long been known that monarch butterflies use sunlight to guide their annual migration across North America. But now researchers have found that the butterflies also use Earth’s magnetic field. According to a new study published in Nature Communications, researchers tested the theory by strapping butterflies into a flight simulator that was surrounded by a magnetic coil system in which the inclination angle of the field could be varied. They found that the butterflies consistently oriented themselves in what they perceived to be a southerly direction—but only when they were also exposed to light in the UV-A/blue range. The researchers believe the butterflies’ directional mechanism lies in their antennae, which contain molecules called cryptochromes that are sensitive to both light and magnetic fields. Although a similar mechanism is thought to exist in birds and sea turtles, butterflies have proven easier to study. The finding is important because the increasing use of electrical devices and AM radios can create an electromagnetic field that could disrupt the butterflies’ migratory patterns.