Circadian rhythms in the antennae of eastern North American monarch butterflies (Danaus plexippus) are integrated to guide the butterflies’ flight paths during migration. These findings, reported in Nature Communications this week, highlight the indispensable requirement of antennae for accurate sun compass orientation and migration.

The antennae of the monarch butterfly are known to be important for migration. These antennae contain light-sensitive circadian clocks, which provide the necessary timing component for successful migration. However, the relationship between each of the two antennae for accurate orientation during migration is unknown.

Steven Reppert and colleagues investigate this relationship further by taking monarch butterflies and painting one intact antenna black, while leaving the other clear. They find that this disrupts sun compass orientation and migration as well as the expression of clock genes. When they remove the blackened antennae, their orientation and circadian clock gene expression is restored, suggesting that even though the events occurring at each antenna are independent, the outputs are nevertheless integrated to allow correct orientation and migration.