The energy is gathered from nectar, and the butterflies that make the trip, those born in the early fall, are able to convert nectar into fat.
“Those born in September know to tank up on nectar,” said Dr. David Marriott, founder of the Monarch Program, a nonprofit research and education organization based in Encinitas, Calif. “Their abdomens get really large.”
Unlike the other generations, these monarchs, he explained, have a little area of fatty tissue where the sugar of the nectar is converted into fat. They can live off this cushion in winter and need only water to rehydrate their bodies.
Monarchs born in September or late August live seven or eight months, sometimes nine, Dr. Marriott said. Their children, grandchildren and great-grandchildren live just a month.
“By the time you get to the great-great-grandchildren it puts us back to September again,” Dr. Marriott continued. The butterflies also feed while migrating, he said.
