What experts think caused the dragonfly swarm in Virginia

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"It is crazy, man... I've never seen so many dragonflies in my life."

Photo courtesy April Ayers Seiple

This has been a familiar scene for many people across southwest Virginia this fall. Scores of dragonflies filled up the evening skies zipping in every direction. Our sister station, WDBJ, received tons of videos from all over the area with many asking, "Why are there so many dragonflies?"

The number of dragonflies was so large that they were even being picked up by radar, including the one here in our area.

So just what caused this spike in dragonflies and why was it so apparent this year?

Entomologists, scientists who study insects, have been looking into dragonflies for awhile. As it turns out, the dragonfly species you saw was likely the common green darner, which is migratory dragonfly.

"It's common that in anywhere from July to mid-October you get these migratory green darners," said Dr. Sally Entrekin, an entomologist at Virginia Tech. "They will lay their eggs in a warmer climate whether it's here or farther south and then the immatures will develop quickly through the winter months."

Dr. Entrekin says there is still plenty of uncertainty in the migration patterns and magnitude of green darners, but a number of studies have been conducted.

It has been reported in these studies that massive swarms follow the passage of cold fronts. Here in Virginia, it appeared the peak swarm occurred during a heat wave right before a cold front, so this makes a bit of sense.

As to why their numbers were so large this year? Dr. Entrekin speculates it may have been a combination of an abundance of resources and a well-timed change in weather pattern.

For those who are afraid of these guys, not to worry; they were just feasting on mosquitoes and other small critters each evening.

We'll just have to wait until next year to see the swarm again.

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