Dragonfly riot

It’s mostly over now, but for a couple of weeks dragonflies were everywhere around our place on Birch Lake, and probably around your lake, too.

Maybe it was the happy coincidence of a dragonfly hatch with the emergence of late-May and early-June mosquitoes. All I know for sure is that the air was full of dragonflies, sweeping up mosquitoes like vacuums on wings.

Though routinely spotted over land, dragonflies are without question water insects – they come out of your lake after a long metamorphosis. The adult stage we see in the air lasts a couple of months, really just a sliver of the insect’s life.

Dragonflies mate while on the wing – no doubt you have seen this act above the water on your lake. The female lays her eggs on a water plant or directly into the water. When the eggs hatch in a couple of weeks, nymphs emerge. They really don’t look anything like dragonflies, but they have one thing in common with the adults: They’re voracious feeders.

Dragonfly nymphs eat all sorts of water insects and insect larvae, and yes, that includes mosquito larvae (call wigglers). So dragonflies are putting a dent in the skeeter population long before they can fly. The nymphs are also quite agile in the water. They swim fast and have a jet-propelled “hyperdrive,” ejecting water from the anal opening.

The nymph stage can last as long as a few years. The nymphs live in your lake’s calm water, amid reeds, cattails and other plants. As they grow, they shed their skin several times. Each in-between phase after the skin is shed is called an instar.

Finally, once fully grown, the nymph climbs up the stem of a plant and emerges from its skin as an adult dragonfly, leaving behind a skin called the exuvia. You may at times have seen one of these clinging to a reed in shallow water. 

And now the dragonfly is ready for serious eating. Dragonflies are so agile in the air that other insects, like gnats, midges, mayflies and, of course, mosquitoes, have no hope of escape. They use their legs like a basket to catch bugs on the wing. Then they feed their prey into their jaws (mandibles) and crush it before swallowing.

How much do they eat? Well, according to dragonfly-site.com, they can eat their own weight in bugs in about half an hour. So that’s why, in mosquito season, we can be thankful to see squadrons of brightly colored dragonflies, sweeping the air around and above our homes and piers.