Dragonflies vs. mosquitoes

The attackers are relentless, determined invaders with one objective: your blood. We weren’t safe anywhere this spring, in a turkey blind or our own backyard. Even the privacy of our bedrooms weren’t immune from their merciless invasion that was signaled by the incoming predators’ high-pitched whine. And then the airborne cavalry arrived to fight them off, and not a moment too soon for northern Wisconsin residents.

This year’s abundance of mosquitos is related to the abundance of rainfall we’ve experienced this spring. Add the dramatic drop in the bat population that began plummeting a decade ago and we were vulnerable. That’s why the arrival of squadrons of dragonflies came at the nick of time.

Some say dragonflies and their close relative, damselflies, are the equivalent of the Top Gun in the insect world. Their agility in the air is unmatched. Not many insects can fly forward or backward, spin 180 degrees in a fraction of a second or fly straight up or down, but with four wings beating between 25 and 45 times a second, they can. These aerial gymnastics are what allows dragonflies to consume up to 100 mosquitos a day each — making a much bigger dent in the mosquito population than bats do — and lessening our burden of dealing with them. Another theory of their ability to maneuver in the air is it makes them difficult to be preyed on by insect-eating birds looking for a meal.

Wisconsin’s home for around 160 species of dragon- and damselflies. Some of them are migrants that come into the state in late summer and early fall when they leave their breeding grounds and head south to find shelter and food for the winter. Researchers point out the migration route for northern Wisconsin dragonflies follow the Lake Superior shoreline, where food and resting spots are readily available.

Not surprisingly, their life cycle involves water, where the females lay their eggs. Actually, dragonflies spend 90-95% of their lives underwater as aquatic nymphs, which is their immature stage. Even these nymphs are predators, feeding on other aquatic insects. At the end of their nymph stage, the nymph crawls out of the water and finds a dry area to go through the change from waterborne insects to the aerial species we commonly associate them with.

The various dragonfly nymphs make the change into adults twice during a Wisconsin summer, depending on the species. Some do this in May and early June when days grow longer and temperatures rise while other species do in late summer. Both adults and young of the year are known to feed heavily on insects. Their hunting skills involve plucking prey from the air by holding their legs like a basket to capture their prey or flying through a swarm of insects with their mouth open wide.

Creating ponds on your property can assist in their life cycle; it’s one way of insuring a healthy population of dragonflies. This may seem counterproductive, since mosquitoes are also water-dependent in their life cycle, but the primary difference is mosquitoes seek out smaller amounts of standing, still water. Buckets, children’s toys left outside, anything that collects small amounts of motionless water is fertile habitat for mosquitos. Although dragonflies require water for their life cycle, leaving some native species of plants for them to perch on is also important. We’re fortunate to have them around to help make those long, beautiful days of summer more enjoyable.