The monarch is one of the best known of all North American butterflies because they make annual migrations across America to avoid winter weather. In autumn, tens of millions fly south and roost in huge numbers on trees in selected mountain areas of California and Mexico. Monarchs will use the same trees year after year.
Monarchs migrate for 2 reasons. They can not withstand freezing weather in the northern and central continental climates in the winter. Also, the larval food plants do not grow in their winter overwintering sites, so the spring generation must fly back north to regions where the plants are plentiful. Their journey can cover up to 2,000 miles before it ends!
