One of the longest journeys in the animal kingdom is undertaken by one of its most fragile creatures: the butterfly. Monarch butterflies migrate from their breeding grounds in Northern Canada down to Mexico for the winter, a 2000 mile flight. Sometimes an individual butterfly will take part in both legs of the journey, but in many species a “parent” generation flies in one direction, and it is the offspring who return.
These aren’t solo trips—migrations are movement on a massive scale. Three thousand million Painted Lady butterflies flew over California in 1924. And a swarm in 1921 over Texas passed overhead at a million butterflies per minute! They don’t let anything get in their way, either: they’ll fly over an object—like a building—instead of around it in order keep on the right trajectory.