North America: dragonfly migration investigated

Green darner dragonflyFrom Science News:

Crouching Scientist, Hidden Dragonfly

Monitoring insect lifestyles in the air and the mud

Susan Milius

When Martin Wikelski and David Wilcove went bird-watching in Cape May, N.J., one fall day in 2004, they were surprised to find that the main spectacle had four wings instead of two.

Migrating dragonflies filled the air, flashing iridescent green and blue as they hovered over dunes, perched, then zipped off. …

Migration biologists have spent decades tracking animals en masse.

Wikelski contends that what’s needed now is an individual bird’s-eye view, or bug’s-eye view, of how migration works.

The migrant dragonflies that Wikelski set about tracking were the common green darners (Anax junius), robust fliers with blue abdomens that turn purple as the temperature rises.

Of the 5,200 species of dragonflies and related damselflies in the world, scientists estimate that 25 to 50 make seasonal migrations.

There’s evidence for migrations among nine North American species.

These aren’t migrations in the bird sense of the word. Each insect makes a one-way trip and another generation returns, scientists presume.

To follow single dragonflies, Wikelski decided on radio tracking.

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