Biology
The Genetic Architecture of Migration Timing in Monarch Butterflies
Quick fact
The timing of the monarch butterfly's fall migration is influenced by a single gene, cryptochrome 2 (Cry2), which encodes a protein that helps regulate the insect's circadian clock. Two specific variants of this gene are associated with butterflies that engage in migratory behavior, and their expression is triggered by shortening day length.
Why this is interesting
Every year, monarch butterflies embark on a 3,000-mile journey to Mexico—but how do they know exactly when to leave? Scientists have discovered the answer is written in their DNA.