When it comes to the world's greatest animal migrations, the movement of millions of wildebeest over vast swaths of savannah probably comes to mind. Or perhaps it's the thousands of miles flown every year by Arctic terns as they move from pole to pole. Or maybe an image of a breeching humpback surfaces in your imagination, as the whales swim from feeding grounds to calving grounds along coastlines.
But what you likely don't think about is the magnificent multi-generation annual migration of a brilliantly colored dragonfly species. Covering thousands of miles on three-inch wings, the common green darner dragonfly completes a multi-generation journey every year.
A recent paper published in Biology Letters reveals for the first time the migration of the species, which provides insight into a bigger issue affecting insect migration.
The researchers showed that darners "undertake complex long-distance annual migrations governed largely by temperature that involve at least three generations."
The first generation begins the journey in spring, moving north where the darners lay eggs and die. Those eggs hatch and the second generation of darners moves south in the fall, where they lay eggs and die. Finally, a third generation hatches to return north the following spring, completing the loop.
This darner species is common, which makes studying it now so important.
"Since migration timing and nymph development are highly dependent on temperature, continued climate change could lead to fundamental changes in the biology for this and similar migratory insects," state the study authors.
Now that there's a handle on how this species migrates, any changes in that process will be much more noticeable.
"With climate change we could see dragonflies migrating north earlier and staying later in the fall, which could alter their entire biology and life history," Michael Hallworth, postdoctoral fellow at the Smithsonian Migratory Bird Center and first author on the paper, told UMBCNews. "Climate change is a threat to all kinds of migration systems, and this could be one of them."
In addition to utilizing museum wing samples and wild specimens, the researchers looked toward citizen science data to analyze migration habits. This data was instrumental in showing that temperature triggers their travel cycle. It's a wonderful example of how helpful public engagement in natural history can be for scientific understanding. Curious about becoming an active citizen scientist? Here are a few ways to get started!