Monarch butterflies (Danaus plexippus) use their internal clock and the sun to guide them 4,000 kilometers south on their annual fall migration from eastern North America to central Mexico. Scientists have struggled to determine how butterfly brains combine visual cues from the sun with molecular timekeeping in their antennae to make the epic journey.
A new mathematical model can effectively mimic monarch flight navigation, researchers argue April 14 in Cell Reports. Their equations for neuron firing rates in the antennae and eyes point to a two-part circuit that orients the insect as the sun’s position changes. As the angle of the butterfly’s body to the sun narrows, it becomes harder for the insect to right itself, the model predicts. While slightly simplistic, the model successfully predicted the movement of live butterflies in the lab.
As the sun’s position changes, monarch butterflies must reorient themselves toward the southwest to stay on their migration track. Researchers tested their new model by turning butterflies in the wrong direction, as shown in this video, and predicting how they might reorient themselves.Reppert Lab, University of Massachusetts Medical School, Department of Neurobiology