Natural History Wanderings

EarthSky reports

Overwintering monarch butterflies rely on a temperature-sensitive internal timer to wake them up to make the trip back north, researchers report.

Each fall, millions of North American monarch butterflies fly thousands of miles and somehow manage to find the same overwintering sites in central Mexican forests and along the California coast.

Once they get there, monarchs spend several months in what’s called diapause, a hormonally-controlled state of dormancy that helps the butterflies survive the winter. An internal timer – like an alarm clock going off – rouses the insects out of diapause, weeks before warming temperatures and longer days, to mate and begin spring’s northward migration.

Read full story at  How do monarch butterflies know when it’s time to migrate? | Earth | EarthSky