Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) The Monarch butterfly is attaining near worldwide distribution in suitable places, but is primarily a species of the Americas. Autumnal migrants occasionally stray to Europe including England; the species has been spread widely in the Pacific Ocean area and is well-established in Australia. However, the seasonal ranges in North America are vastly different, by millions of square kilometers. Essential overwintering areas for North American populations are limited to a few dozen places in coastal California and the mountains of Mexico. Specifically that means that the summer range includes portions of up to 49 of the 50 US states and southern portions of all Canadian Provinces bordering the US where milkweeds occur. However the winter range includes none of Canada and in the US only a few dozen square kilometers in California, and at least some years a bit of south Florida. Florida winter populations may be non-migratory and if so contribut little to summer populations. Some winters a few may persist in sothern Arizona.
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