Every autumn, monarch butterflies from west of the Rocky Mountains journey to California to wait out the winter.
Each black-and-orange insect weighs less than a raisin, yet together they traverse thousands of miles over mountains and valleys, across cities and suburbs, toward a shrinking network of coastal groves that provide the right microclimate for their survival.
Western monarchs’ epic migration spans up to 1,000 miles each way. Monarchs are rare among insects in that…