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There are few more awesome sights in the animal world than the seasonal mass migrations of the monarch butterfly, Danaus plexippus, from the northern United States and southern Canada to its overwintering grounds in central Mexico (1). As with other insect orientations, the monarch uses the position of the Sun to calculate where it should be going. However, as the Sun moves across the sky during the day, the monarch must continuously adjust its calculations, which it does by using its 24-hour circadian clock. So where is this time-compensated clock located? On page 1700 of this issue, Merlin et al. reveal that it's in the antennae (2).