astralavista

Czech and American scientists have discovered the navigation gear that steers monarch butterflies on their annual pilgrimage from the north of the United States to Mexico. It's been known that the miniscule machinery resides in the monarch brain and guides the insect by analyzing the angle of polarized ultraviolet sunlight. But the researchers found that the key to the system is a link between the insect's eye and the brain region that holds the circadian clock circuits. The link, which the scientists spied by using tracer molecules illuminating circadian neural fibers connected to polarization photoreceptors in the eye, allows the butterflies compensate its position and flight path for the time of day. "This pathway has not been described in any other insect, and it may be a hallmark feature of butterflies that use a time-compensated sun compass," the researchers wrote. Since the link also supplies the brain with information about daylight, the scientists speculate that it might launch the monarchs's autumn migration. "The decreasing length of the day in the fall appears to be an important determinant for stimulating migratory behavior in butterflies," they said.
Of course, they went on to test their discovery and placed UV interference filters over the polarized light source simulating the sun in the lab. Sure enough, the poor monarchs got lost.