Dragonfly swarm stops in Southwestern Pennsylvania | TribLIVE.com
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Jamie Martines

Not a bird, not a plane: Dragonflies are swarming the skies over Southwestern Pennsylvania.

The insects have been observed throughout the region over the past week, touching down to refuel before continuing their yearly migration toward Central and South America.

“Swarms are great for cutting down the small insect population, those biting insects we don’t like,” said Chris Goforth, head of citizen science at the North Carolina Museum of Natural Sciences.

Goforth also leads the Dragonfly Swarm Project, an effort to determine how and why dragonfly swarms form. She has crowdsourced over 7,000 swarm observations with the help of fellow insect enthusiasts across the country since 2010.

“Migration is really complicated,” Goforth said. “It’s hard to figure out ways to tag dragonflies and follow them.”

As a result, scientists don’t know much about where the dragonflies are going and how they choose pit stops along the way. Goforth said weather patterns play a role, since dragonflies are attracted to wet, humid areas that are also likely to have large populations of prey — mosquitoes, black flies and other small insects.

Regions that have experienced big storms or flooding are likely to experience dragonfly swarms this time of year, she said. But even then, it’s hard to predict exactly where and when the mysterious insects will show up.

“You have to be at the right place at the right time to see it,” Goforth said of the elusive swarms.

The National Weather Service in Cleveland observed the swarms earlier this week over Indiana, Ohio and Pennsylvania.

In a radar image shared by the agency Sept. 10, the swarms look like giant, florescent jellyfish pushing through the region.

Lee Hendricks, a meteorologist with the National Weather Service in Pittsburgh, said the insects have been showing up on local radar for the past week.

“We couldn’t tell you exactly what it was by seeing it on the radar,” Hendricks said, noting that meteorologists are able to determine when objects detected by the radar are not related to weather.

For example, weather radar detects ducks and geese taking off from area lakes around sunrise nearly every day, Hendricks said.

The region’s spring cicada swarm did not appear on the radar because those insects flew too low to be detected, Hendricks said.

The swarms likely include Green Darner dragonflies, which can reach about three inches long and can be found in the Pittsburgh region’s ponds and wetlands, said Scott Detwiler, an environmental educator with the Audubon Society of Western Pennsylvania.

Males can be spotted by their blue abdomens, while females are typically green or brown.

Baby dragonflies, called nymphs, are found in fresh water.

Detwiler suggested trekking to any local meadow, park or grassy area to observe the insects while they’re still in town.

Keep your eyes peeled for hawks — which may eat the dragonflies — along with monarch butterflies, which are also migrating this time of year.

Anyone interested in sharing their observations with Goforth and the Dragonfly Swarm Project can contribute online at thedragonflywoman.com/dsp.

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