Search NOVA Teachers

Back to Teachers Home

The Incredible Journey of the Butterflies

Program Overview

NOVA traces the monarch butterfly's 2,000-mile migration to Mexico from Canada and the Northeastern United States.

The program:

  • shows how a caterpillar changes into a butterfly.

  • notes that it takes four generations to make the entire round trip—one generation flies from Canada to Mexico, followed by three more generations that complete the return trip and year-long cycle.

  • states that no one knows what triggers the exodus from Canada or how the monarchs know how to navigate to Mexico.

  • presents the threats monarchs face on their journey south, including predators and bad weather.

  • points out that the monarchs are able to make the long trip by soaring on thermals and describes how thermals are formed.

  • provides maps that chart the migration's progress.

  • visits the monarch's destinations, where the local Mazahua people believe that the arriving butterflies carry the spirits of their ancestors.

  • explains that the monarchs rely on the Mexican mountain forest because its canopy keeps the heat in and the rain out, and its large trees retain and radiate heat the butterflies need to survive during their overwintering.

  • reports that while it is not fully understood how monarchs know where to migrate, scientists have proposed theories that the trip could be influenced by the sun's angle in relation to Earth or that Earth's magnetic field provides a subtle orientation guide.

  • introduces Monarch Watch, started in 1992, which recruited teachers and students to tag butterflies in the northeastern United States.

  • explains how monarchs that were moved from Kansas to Washington, D.C., were able to reorient their course and head in the correct direction to Mexico.

  • reveals that illegal logging is endangering the Mexican forest where the monarchs migrate.

  • features the monarchs' arrival at their Mexican destination, where they will overwinter for almost five months before beginning the first leg of the journey back to Canada.

Taping Rights: Can be used up to one year after program is recorded off the air.

Teacher's Guide
The Incredible Journey of the Butterflies?

Support provided by