Following the Monarchs

• ○A. It describes a migration route shared by monarchs throughout the world.
• ○B. It focuses on eastern monarchs while recognizing that other patterns exist.
• ○C. It compares the distances traveled by monarchs from several continents.
• ○D. It focuses on monarchs that remain near their breeding grounds all year.

A monarch passing over a field may be making more than a short trip between flowers.Each fall, many monarchs from eastern North America travel south to mountain forests in central Mexico.Some begin their journeys in the northern United States or southern Canada, far from their winter destination.This article follows that eastern migration; monarchs in other regions may follow different routes or remain in one area.

• ○A. Adults leaving Mexico reach northern areas before laying their eggs.
• ○B. The northward movement takes place without new butterflies joining it.
• ○C. Summer arrivals in northern areas usually spent the winter in Mexico.
• ○D. The northward movement continues across the lifetimes of several generations.

The journey north unfolds differently from the fall trip south.After winter, surviving adults leave Mexico and fly north, laying eggs on milkweed along the way.Their offspring continue the northward movement, and later generations spread farther across the breeding range.Thus, the monarchs arriving in northern areas in summer are generally descendants of the butterflies that left Mexico, rather than those same individuals.

• ○A. They could support migrating adults by providing places to refuel.
• ○B. They could replace the wintering forests by providing warmer shelter.
• ○C. They could feed caterpillars even if the fields contain no milkweed.
• ○D. They could let adult monarchs complete the journey without further food.

Long-distance travel requires fuel, even for an insect that can glide on rising air.Adult monarchs drink nectar from flowers, including flowers they encounter during migration.A flowering patch beside a road or in an open field can therefore serve as a feeding stop between distant destinations.Milkweed has a different role: monarch caterpillars eat its leaves, so breeding females need places where it grows.

• ○A. It supports the claim because the fall travelers have not visited Mexico before.
• ○B. It supports the claim because following the sun explains the entire journey.
• ○C. It challenges the claim because some parts of locating the destination remain unexplained.
• ○D. It challenges the claim because researchers have found no useful navigation clues.

A southbound monarch cannot follow an older butterfly that remembers making the entire trip before.The fall travelers belong to a generation that has not previously visited the wintering grounds.Research shows that migrating monarchs use the sun, together with an internal clock, to help maintain their direction as the sun changes position.Scientists have learned important parts of this navigation system, but they have not fully explained how monarchs locate particular wintering areas.

• ○A. Cool conditions let monarchs spend more energy flying between trees.
• ○B. Cool conditions can help monarchs make their stored energy last longer.
• ○C. Cool conditions cause monarchs to replace nectar with leaves for food.
• ○D. Cool conditions allow monarchs to survive without shelter from trees.

In Mexico's mountain forests, monarchs gather in large groups on trees.Cool conditions help them use their stored energy slowly during the winter months.However, severe cold combined with wet conditions can threaten their survival.Forest cover helps shelter the butterflies, making the condition of the wintering habitat important even when the insects are not traveling.

• ○A. The butterfly visited the location where researchers first attached its tag.
• ○B. The butterfly traveled between the tagging location and the recovery location.
• ○C. The butterfly's record could be combined with records from other recovered tags.
• ○D. The butterfly flew between the two recorded locations without stopping anywhere.

Researchers study migration through observations, counts, and the recovery of tiny numbered tags attached to some butterflies.A tag recovered far from its starting point connects two locations visited by one individual.However, those two locations do not reveal every place the butterfly stopped between them.By combining many records rather than treating one recovery as a complete travel diary, researchers build a fuller picture of the migration.