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What Time is it in Nature: Dragonfly Swarms

September 15, 2012

Dragonfly Swarms

You will typically find dragonflies by the Prairie Ridge pond or stream, but every now and again you’ll see a lot of them forming a dense swarm out over the prairie.  This fascinating behavior is rarely observed by people, but swarms occur fairly regularly at Prairie Ridge.  Keep an eye out for dragonfly swarms when you visit!

dragonfly swarm

What is a dragonfly swarm?  Dragonfly swarms are groups of dragonflies (10 – 1,000,000 dragonflies) flying together away from water.  Though there is a lot of variation in swarm size and timing, swarms are most often reported at dusk and typically last an hour or less.

Why do dragonflies swarm?  Dragonflies swarm for two reasons.  Dragonflies are predators so if there is abundant food in the area, i.e. lots of small flying insects such as mosquitoes or other flies, a swarm may form in the same area.  In these static swarms, the dragonflies fly back and forth over a specific, well-defined area, eating the small flying insects within that space.  Dragonflies also migrate, so you might see large groups of them flying together in a single direction, either to escape poor local conditions (dry, very hot) or to seek warmer regions in the fall.  Migratory swarms can contain several million dragonflies and travel thousands of miles!

Why should I care about dragonfly swarms?  There is evidence that static dragonfly swarms commonly appear after flooding has occurred in an area.  Because dragonfly swarms form where there is an abundance of food available, these swarms are likely very important in regulating the population boom of mosquitoes and other biting insect pests that occur after flooding.

Can I help researchers learn about dragonfly swarms?  Yes!  If you see a swarm, you can report it to The Dragonfly Swarm Project.  More information about The Dragonfly Swarm Project, including an online report form, is available at

Dragonfly swarms have been reported several times at Prairie Ridge, so it’s a great place to look for them.  Come on out and see if you can find one!

What Time is it in Nature is a weekly feature highlighting the current plants, animals, and other wildlife at the Musuem’s public outdoor facility, Prairie Ridge Ecostation.  Find out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive!

(Photo by David Alexander)

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