Praxis 5001 Practice Test 15

Monarchs on the Move

A Long Journey

Each fall, millions of monarch butterflies leave the northern United States and Canada and fly as far as 3,000 miles to forests in central Mexico. No single monarch makes the whole round trip. The butterflies that fly south in the fall are the great-grandchildren of the ones that left Mexico the spring before. This yearly migration is one of the longest made by any insect.

Finding the Way

Scientists think monarchs use the position of the sun to steer. Because the sun moves across the sky during the day, the butterflies also rely on an internal clock that keeps track of the time of day.

Threats to the Migration

Monarch caterpillars eat only one kind of plant: milkweed. Female monarchs lay their eggs on milkweed leaves so that the caterpillars can feed as soon as they hatch. When farms, roads, and lawns replace fields of milkweed, fewer caterpillars survive. Milkweed has a milky sap that gives the plant its name. Long stretches of hot, dry weather can also wither the nectar flowers that adults need for energy, so fewer butterflies complete the trip. Many families now plant milkweed in their gardens to help.

Glossary — migration (noun): the regular movement of animals from one region to another and back, usually with the seasons.