If you have ever been to a lake you may have seen dragonflies, their iridescent bodies reflecting the sunlight as the insects rest on the leaves of water plants or flit about on their four strong wings.

But have you ever seen a swarm of dragonflies? If you do, don‘t be alarmed. Instead, be grateful because these insects are probably feeding on mosquitoes – so there are fewer mosquitoes to feed on you!

Dragonfly History

Dragonflies are ancient insects, the earliest fossils are more than 300 million years old. These fossils show that prehistoric dragonflies had wingspans that were two and a half feet and up and weighed about one pound. These prehistoric dragonflies were carnivores, much like their modern descendants: They feasted on other insects and perhaps even small amphibians.

As the oxygen content of our atmosphere decreased, insect size followed suit. Eventually, insects could only grow to the size we know today. At their current size, the diet of the dragonfly is limited to much smaller prey - which is why mosquitoes are a favorite dish.

Why Do Dragonflies Swarm?

Scientists don't fully understand this swarming behavior. Although, there is some agreement that dragonflies swarm because their food sources swarm. If it has been a rainy season, or if you live near a lot of standing water, then the mosquito population is bound to be booming.

If a large mosquito population is present at the time and place of the emergence of fully grown dragonflies (usually late July to early August) then you may witness a dragonfly swarm.

Dragonflies do not only eat mosquitoes, so you may even catch a small swarm of dragonflies in your yard if there happen to be any acceptable prey abundant there.

Fueling A Short Life

Once a dragonfly has reached its adult form, it doesn‘t have long to live – only weeks to months. During this short life span, a dragonfly is a voracious hunter. Dragonflies are versatile fliers, they can move in all directions and even hover. They use this versatility along with amazing speed and 360-degree vision to consume their own weight of insects in just thirty minutes.

Want to see a dragonfly swarm? Flooding in Missouri this summer has created immense swarms of insects dubbed "bugnadoes" and dragonflies have been seen taking advantage of these high concentrations of prey.

Have you seen a swarm? Contribute to The Dragonfly Swarm Project, a project undertaken by an entomology graduate student at the University of Arizona who hopes to increase our understanding of dragonfly swarms.

Read More:

Dragonflies Hunt Mosquitoes (Victoria Advocate)

Studying Dragonfly Swarms (scienceforcitizens.net)