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The Boston Globe



A titan on orange wings

How does the monarch migrate 2,500 miles?

If there is such a thing as visual clamor, that’s what monarch butterflies have been creating in my backyard for the past few weeks. They demand to be looked at. They’re so big, so graceful, so luminous, and so plentiful, that whenever I’ve gone outside with a book I’ve ended up watching the monarchs. On sunny afternoons there are dozens of them hovering and alighting on the purple buddleias (one bush is some fancy variety I planted, and two are just big weeds; but the butterflies don’t seem to care whether they’re drinking champagne or beer from the can). Their abundance this year made me suddenly curious to learn more. When I look at a monarch in my garden, what exactly am I seeing?

Not some fragile, ditzy little creature, that’s for sure. One of the first things you learn when you start asking about monarchs is that they migrate. The individuals who seem to be whimsically flitting around my garden are actually on their way to Mexico for the winter. How an insect has the strength to fly 2,500 miles is a mystery. How it navigates is even more mysterious. New Hampshire naturalist Davis Finch told me that while on a boat observing seabirds he has seen great flights of monarchs 20 to 30 miles offshore. “They don’t go in flocks, but they are all headed in the same direction. It’s very organized. They have the knowledge in their genes.” Scientists have posited that monarchs rely on sun angles, or visual cues such as coast- and ridge-lines, or an internal magnetic compass.

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