AUGUST 24, 2009
Have you seen any monarch butterflies lately? Now is the time to spot them on their annual southern migration, which in North America starts in August and lasts until the first frost. I photographed this one at the botanical gardens in Montreal, Quebec.
The monarch is the only butterfly that migrates both north and south, as the birds do on a regular basis. No single individual makes the entire round trip, however, since the length of the journey exceeds the normal lifespan of most monarchs, which is less than two months for butterflies born in early summer. According to Wikipedia, it is the second, third, and fourth generations of the insect that return to northern locations in the US and Canada. How the species manages to return to the same overwintering spots over a gap of several generations is not clearly known, but its flight patterns appear to be inherited, based on a combination of circadian rhythm and the position of the sun in the sky.