As summer wanes into autumn and the cooler weather starts to roll in, what happens to the dragonflies that hatched out of our local waterways over the last few months? Well, the answer is a little bit different for each species.
These insects (and many more) spend a portion of their lives in the water. Dragonflies are a good indicator of water quality as some species are more tolerant of pollution and others are very intolerant of pollution. Many aquatic insects also have very specific habitat needs, so knowing which groups are found in a stream and which ones are missing helps guide restoration projects. Back to the dragonflies and where they go…
Laying Low During the Winter
During the summer months, dragonflies emerge from their aquatic larval stage, stretch out their wings and take flight. Females and males tend to use different habitats until it is time to mate. Here is where some species differ in their approach to surviving winter – some lay eggs in the water that will hatch, grow underwater through the summer, slow down for the winter and then emerge as adult dragonflies the next summer. Some of these species may stay in the aquatic larval stage for several years before emerging as adults, like the federally endangered Hines Emerald Dragonfly that is found in parts of the Des Plaines River Watershed.
Other species of dragonflies and damselflies will lay eggs that survive the winter and hatch the next spring or summer. They lay their eggs in vegetation or damp logs along the edge of a pond that will be inundated in the fall or spring, triggering the eggs to hatch and start the larval journey. The Swamp Darner uses this tactic, laying its eggs in logs in ephemeral ponds that dry out in the summer and fill back up in the spring.
Many other aquatic insects follow this same life cycle. They emerge as adults in the spring or summer and either lay eggs that hatch and spend the winter in the larval stage or lay eggs that overwinter and hatch the next spring or summer.
Did You Know Some Dragonflies Migrate?
One strategy to surviving the winter that we don’t usually think about when it comes to dragonflies is heading south for the winter! A few species of dragonflies actually migrate – the most common one is the Green Darner, a large, colorful dragonfly.
Like the Monarch Butterfly, the Green Darner migrates over three generations. They emerge from waters in the Gulf Coast, Florida and the Caribbean and fly upwards of 400 miles to the north where they lay eggs and die. The eggs hatch, the larvae grows and emerges in mid to late summer. These adults form large groups and fly back south where they lay eggs and die. Another generation grows, emerges, lays eggs in the south and dies without migrating at all. This last set of eggs will hatch out and travel back up north, starting the process all over again.
Want to learn more about dragonfly migration? Here is a link to a great article that describes the scientific techniques that researchers used to determine where the dragonflies migrated from.
At a Glance
- Different species of dragonflies tolerate different levels of pollutants in a stream or have different habitat requirements. Because of this, dragonflies are important indicators of waterway health.
- Some dragonflies spend the winter underwater in their larval stage. Other dragonflies lay eggs that survive the winter and hatch the next spring or summer.
- A few species of dragonflies, like the Green Darner, migrate south for the winter and lay eggs. This next generation stays in the south for its entire life cycle. The third generation will migrate back north.