Monarch butterfly

The butterfly that flies 4,000 km

Every autumn the monarch butterfly flies 4,000 km from Canada to Mexico — like Tashkent to Paris! Millions of butterflies land on the trees of one forest, and the trees turn orange. The most amazing part: the butterfly making the journey has never been there — not even its grandpa taught it, it just knows the way!

The monarch (Danaus plexippus) is North America's migratory butterfly. In autumn it flies 4,000 km south to overwinter by the millions in a few hectares of oyamel fir forest in the mountains of Michoacán, Mexico. The spring return north takes 3–4 generations: each lives 4–6 weeks, and only the autumn 'super generation' lives 8 months and makes the whole trip. It navigates with a sun compass and an internal clock. The caterpillar eats only toxic milkweed and stores the poison — its orange colour warns birds. Because of milkweed loss and deforestation, numbers have fallen 80% since the 1990s.

Fun facts

• A monarch flies 4,000 km — and weighs just half a gram!
• The butterfly that reaches Mexico has never been there — it's following its great-great-grandmother's route.
• When millions of butterflies land on a tree, branches can break under their weight.