Every November, millions of Monarch Butterflies fly up to 5,000 km from southern Canada and the United States to their winter homes in Mexico's Sierra Madre mountains. A few will overwinter along the coast of California or the Gulf coast, but most will end up perched in clusters (to stay warm) on fir trees in Mexican forests.
Monarchs have orange wings with black veins and a double row of white spots within a thick black border (3.5-4 in wingspan). They lay their eggs on Milkweed plants, almost the only food eaten by the caterpillars. The 2-in long caterpillars have bright black, yellow, and white stripes. After feeding on the leaves for 2 weeks, the caterpillars attach themselves to a twig, shed their outer skin, and form a hard light-green coating, from which the butterfly emerges in 2 weeks' time.
Only Monarchs born in late summer or fall will make the migration. Many generations will have been born and died before the Monarchs migrate again the next year and yet somehow they remember the route and the destination.
Could it be? Painted Lady Butterflies are also orange and they migrate to Mexico as well. However, they have splashes and dots of black and white on their wings rather than black veins.
Did you know? Birds and other predators know that Monarchs taste horrible and stay away. The predators also avoid butterflies that mimic the Monarch, such as the Viceroy.
See Also: Admiral Butterfly, Azure Butterfly, Banded Woolly Bear Caterpillar, Cabbage White, Clouded Sulphur, Compton Tortoiseshell, Great Spangled Fritillary, Hawk Moth, Mourning Cloak, Painted Lady, Tent Caterpillar, Tiger Swallowtail