The study conducted by researchers in Baltimore County, published in Biology Letters, reveals the annual migratory cycle of the green darner dragonfly. Using stable hydrogen isotope analysis on wing samples from over 800 dragonflies collected over 140 years, the study found that it takes three generations to complete the cycle. The first generation migrates from the southern United States, Mexico, and the Caribbean to the upper Midwest between February and March, lays eggs, and dies. The second generation matures and migrates south, laying eggs upon arrival. The third generation does not migrate but lays eggs that restart the cycle the following spring.

What method did researchers use to study the migratory cycle of the green darner dragonfly?

• Satellite tracking

• Stable hydrogen isotope analysis

• Radio telemetry

• Genetic sequencing

Where do the first generation of green darner dragonflies migrate to by May?

• Upper Midwest

• Southern United States

• Mexico

• Caribbean

What happens to the first generation of dragonflies after they lay eggs?

• They migrate further north

• They return south

• They die

• They remain in the Midwest

What is the primary activity of the second generation of dragonflies?

• Staying in the Caribbean

• Migrating south

• Laying eggs in the Midwest

• Migrating north

What is unique about the third generation of green darner dragonflies?

• They migrate to the Caribbean

• They lay eggs in the southern United States

• They do not migrate

• They migrate to Mexico