Page 112 - The Miracle of Migration in Animals

Above: Major trends of monarch butterfly migrations in North America. The
monarchs move northward in spring and lay eggs during the journey. They
travel an average of 15 kilometers (9 1/2 miles) per day. Subsequent genera-
tions make longer and faster journeys back to the south without breeding.

will live six months longer than the others, and in this way the chain
will continue.
Why is one generation in four born with the characteristic of liv-
ing six months longer? Why are these particular longer-lived butter-
flies hatched just ahead of the winter months? Why do they begin

their migration at the equinox, and how can they make this fine cal-
culation? How does a newly emerged monarch know the way, on a
route it has never flown?
The answer to all these questions is that monarch butterflies
have been created in accordance with a perfect migration plan and
conform to it to the last detail. If there had been the smallest flaw in
this plan, from the time these insects came into being, monarchs
would not have completed their migration. Winter would have killed

110