Dragonflies and monarchs: multi-generation migrations

Dragonflies are a common sight during Canadian summers—zooming around the skies to catch their insect prey and darting around wetlands, laying their eggs in and around the vegetation. But as summer weather turns to fall, species like the common green darner begin their journeys south.

Dragonfly migration

Unlike bird migration, the dragonflies that leave from the north are not the same individuals that return the following spring. Instead, their round-trip travels can require three generations:

• One that emerges from larva in the north—then migrates, breeds and dies in the south.
• One that emerges from larva in the south and does not migrate. This generation breeds and gives rise to the following generation.
• One that emerges later from larva in the south—then migrates, breeds and dies in the north.

Until recently, dragonfly migration was not well understood. But research published in 2018 detailed the journeys of common green darners, using analysis of 852 wing samples from eight countries, along with citizen science observation, to link each to its birthplace and establish their migration history.

Monarch migration

Monarch butterflies in Canada spend their summers on and around flowers like milkweed, both feeding and pollinating the plants. They cannot survive Canada’s cold winter weather, and so begin a two-month journey south in late summer, travelling to California or Mexico. This generation of migratory monarchs—the one that completes the species’ fall migration—lives longer than those that are born in winter ranges and migrate north in spring.

In early spring, monarch butterflies begin migrating north. It can take up to five months, covering 3,500 kilometres, and may involve multiple generations as they stop and breed along the way. The butterflies that arrive in Canada give rise to the generation that will eventually complete the next journey south.