Monarchs use Earth's magnetic field to navigate

The two newly-hatched monarchs on my fingers above nectared in our yard for a while after release last summer, then eventually headed toward Mexico.  It has always been taken for granted that butterflies use solar orientation for navigation.  Now some recent research indicates that they, like birds, may also incorporate a system of geomagnetic detection:

The research team used fruit flies engineered to lack their own Cryptochrome (Cry1) molecule, a UV/blue-light photoreceptor already known to be involved in the insects' light-dependent magnetic sense. By inserting into those deficient flies butterfly Cry1... the researchers found that either form can restore... magnetic sense in a light-dependent manner, illustrating a role for both Cry types in magnetoreception.

The research is described in their paper, "Animal cryptochromes mediate magnetoreception by an unconventional photochemical mechanism," posted on-line in the journal Nature on January 24.