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Swarm of Dragonflies

Oakdale, Minnesota, a suburb east of Minneapolis/St. Paul. Single-story townhouse complex surrounded by deciduous swamp.

On August 29, 2013, about 7 p.m. Central Daylight time I watched a swarm of dragonflies. I saw 20 to 40 of them. The largest looked to be about 3 inches long. Others looked a little smaller. Through dark gray polarized sunglasses (my corected vision is about 20/30, a little worse than normal but not much) they looked to have blue and black colors but I wouldn't trust that description.

They were flying on the edge of a cattail and canary reedgrass swamp with brush at the edge, over a trimmed lawn and the roofs of the buildings. They swooped in an irregular pattern, coming down to about 5 feet and rising to about 20 feet over the roofs. The swooping reminded me of swallows catching insects over a pond.

I walked around the complex but didn't find them anywhere else but in this 40 to 50 foot stretch.

The swamp is probably pretty dry after a wet May and June but we up to a half inch of rain after midnight this morning. There is a small creek flowing through the swamp about 75 to 100 yards away from the swarm.

Without a photo I'd be amazed to get an identification.

My question is: What were they doing?


Roxie Aho

Probably a feeding swarm of t
Probably a feeding swarm of the genus Aeshna (darners), maybe with others mixed in. It could have been several different species. They were probably feeding on swarms of tiny insects coming out of the wetland.

 
Yep
Sometimes, when you catch a ray of afternoon light at the right angle, you can see swarms of tiny bugs (gnats, ants, midges) hovering around or moving slowly upward. Someone coined a great term for these congregations - aerial plankton. Dragonflies, especially darners and gliders, seek out these swarms like sharks seek out schools of anchovies.

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