Dragonflies go through marvelous metamorphosis along the St. Croix River

Researchers looking for the intriguing insects on the upper river were lucky to see special species and amazing transformations.




11 minute read

A Skillet Clubtail (Gomphurus ventricosus) which recently emerged from the St. Croix and its exoskeleton perches on the banks of the river as its wings harden for flight.

Dragonflies are defining features of summer days on the St. Croix, buzzing beaches and boats. They are acrobats In the air, the envy of helicopter pilots, able to fly fast and turn sharply, hovering and flying sideways and even backwards as they pick off their insect prey mid-air.

They are big, colorful, and ferocious, and can capture anybody’s curiosity.

Kids are especially enraptured by the bulging eyes, jutting jaws, and aerial antics. Dragonflies’ unmatched flying abilities, remarkable eyes, and other adaptations, make them almost perfect predators.

Dragonflies were some of the first insects to evolve about 300 million years ago, when a relative with two-foot wingspans hunted humid jungles. Higher oxygen levels in the atmosphere at that time helped the hawk-sized insect grow so large.

Fierce and friendly

Cobra Clubtail (Gomphurus vastus)

Many times, dragonflies have landed on my canoe or kayak while I float down the St. Croix and its tributaries, resting and riding along. Their mix of ferocity and friendliness is intriguing, and it seems like they come in endless combinations of sizes and colors.

I always want to know what I’m seeing, if it’s common or rare, what its presence says about the river, what its life is like, and how it fits into the whole ecosystem.

This curiosity is how I connected with some members of the Minnesota Dragonfly Society: Mitch Haag, Curt Oien, and Ron Lawrenz. I’ve tagged along with them previously around Marine on St. Croix, as well as the Red Lake Peatlands of northern Minnesota..

One late May day, we headed to the upper river to canoe and hopefully see some interesting species.

When I met up with them in the morning at Stevens Creek Landing, east of Rush City, the temperature was in the 50s and the sky was overcast and threatening to rain. Those were discouraging conditions to look for cold-blooded dragonflies. The bugs are most active on sunny days. When it’s warm, they are in top form and can pick off other insects easily, fueling their flight.

Then we discovered they were actually abundant — just not in the air.

Instead, the banks hosted a bonanza of dragonflies going through the biggest change of their lives.

Lethal larvae

A nymph from the Darner family, one of the most effective aquatic predators.

Dragonflies are unique in their excellence at hunting both in the air, and underwater.

During the first part of their lives, which can last from a couple months to several years, a dragonfly grows from an egg to a hard-shelled nymph on the bottom of lakes and rivers. In that stage, the insects are expert hunters, ambushing other aquatic creatures, gobbling up other insect larvae, tadpoles, and even minnows.

A dragonfly larvae’s most lethal adaptation is “liquid propulsion,” which really means they move around by squirting water out their butts. Their gills are located in the same internal chamber in their rear-ends, and its muscles can either pump water over them to get more oxygen, or push the insect forward at a speed of about 4 inches per second.

Finally, when it is time to mate, the underwater bugs are born into the atmosphere, and only after shedding their aquatic exoskeletons.

Molting takes a while. Dragonflies must extract themselves from their shell and then pump “hydraulic fluid” into their wings to straighten them out, then let the wings stiffen enough to create lift.

Extra hemolymph, the liquid which is pumped into veins in the wing to shape them, drains out of a Rusty Snaketail as it prepares for flight.

Only then can they fly somewhere safer.

Hours pass when the ferocious predators are vulnerable, unable to move, easy prey. At the beginning of a dragonfly’s life, it is threatened by fish. In the air, birds are the main enemy. But at both those stages, the insects’ amazing eyes and high-speed maneuvering help them survive.

In the middle, they are immobilized and defenseless, and seemed to have a single-minded focus on their transition.

That also meant they were easy to observe and photograph, not flying away at our approach. The researchers didn’t have to try netting them out of the air, but could pick the flightless bugs up and hold them while comparing their details to the identification guide.

Mass metamorphosis

Rusty Snaketail (Ophiogomphus rupinsulensis) emerging.

On this gray, cool day, we discovered that almost any little place the juvenile insects could, they were climbing out of the watery world that was the only one they had ever known, crawling a few feet and finding a spot to transform.

We speculated that a low-pressure system moving through might have been spurring them to emerge today. We wondered what else it could be.

And we watched as they burst out of their bodies and prepared for their first flight, and the final stage of their lives.

Mitch and Curt have day jobs with the Three Rivers Park District in the western Twin Cities, and Ron is director of Warner Nature Center in Marine on St. Croix. All three have spent a lot of time searching for dragonflies. They all think highly of the St. Croix.

During a rare pause in the action, Mitch recalled canoeing on the river years before. In the stern of the boat, he had his paddle in one hand and net in the other. While his wife was enjoying the peaceful float from the bow, her partner swung wide to nab a dragonfly, leaned too far, and swiftly overturned the canoe, dumping his bride in the water with no warning.

Mistakes happen.

Older and possibly wiser, still passionate about dragonflies, Mitch said he had never seen conditions quite like what we encountered.

Counting clubtails

A female Rapids Clubtail (Gomphus quadricolor)

Most of the species we saw were called “clubtails,” or in Latin, the Gomphidae family. They get their name from the bulge at the end of their skinny abdomens. With specific habitat requirements and a relatively short time when they are airborne, clubtails can be something special to see.

The St. Croix’s namesake dragonfly is the St. Croix Snaketail — a branch of the clubtail family.

We didn’t see any of those rare creatures, but there were innumerable Skillet Clubtails and Pygmy Snaketails and much more, clinging to the dry ground while they transformed.

Rapids Clubtail (Gomphus quadricolor) emerging on the banks of the St. Croix.

“I’ve never seen so many skillets in my life,” Mitch said. “And more adult howei [pygmies] than I’ve ever seen.”

These species are usually an infrequent sighting, because adults can spread out across large areas once their wings are working. But this day they were plentiful, scattered densely on the banks, spurred by some natural signal to molt en masse.

“It’s like the whole population is emerging today,” Mitch said.

We were only planning to drop a car at Stevens Creek, head six miles upriver, and canoe back down, but it took us a while to tear away from the banks at the landing. Just when we would go to leave, another insect would catch someone’s eye, and it was examined and identified.

Then when we were really about to get in the cars, Mitch found a cold and lethargic Eastern Hognosed Snake. It too would have liked the weather to warm up.

Specimen skepticism

Identifying Odonata (the scientific name for the dragonfly family).

When we finally got to our put-in landing at the Snake River, the scientists once again surveyed the banks, and once again found an abundance of Odonata. Walking through the water, they stooped over frequently to inspect an insect.

Telling different species of dragonflies apart is not always easy. It can mean studying the spots on their body segments, examining the tiny appendages on the end of their body, or comparing mouth parts or the eyes. The researchers kept their copies of Kurt Mead’s Dragonflies of the North Woods handy while on the hunt and worked through a process of elimination with every intriguing specimen.

They seemed to most enjoy it when they could not immediately determine the species. In a microcosm of the scientific process, they would debate their identifications, forcing themselves to a high standard of skepticism.

Mitch, Ron, and Curt (left to right) admire a specimen.

After the area around the landing had been inspected, we launched the canoes, but we didn’t start heading back downstream to our cars, instead paddling upriver 100 yards to the mouth of the Snake River.

Once again we were greeted by a plethora of young dragonflies, and we were in and out of the canoes, searching for specimens.

By the time we finally turned our attention and our boats downstream, a few hours had elapsed since morning. Our plan to paddle canoes about six miles down the river, trying to net dragonflies “on the wing,” seemed silly when all the action was on the banks. A new plan was made.

Back at the landing, having made no progress by paddle, we loaded up the canoes and drove downstream to survey another site on foot. For the rest of the afternoon we waded along shorelines, continuing to encounter a bounty of bugs.

River Styx and the St. Croix

Stygian Shadowdragon (Neurocordulia yamaskanensis)

At the Highway 70 landing, the group found a hard-to-find highlight: A recently-emerged Stygian Shadowdragon (Ron also found a nymph of the species in the mouth of the Snake River).

The dragonfly’s name evokes its dark coloring and the River Styx, the ancient Greeks’ border between the Earth and Hades, the underworld. You can picture them patrolling that river, where the living passed over to the world of the dead.

Stygian Shadowdragon are crepuscular — only flying for about a half-hour each day right before dark, perched and hiding the rest of the time, possibly in the treetops.

“During this short time of flight they are extremely active,” wrote Canadian biologist E.M. Walker in 1915, observing them on the shores of Georgian Bay on Lake Huron. “They dash about erratically over the rocks among the swarms of mayflies and when one of these is captured they retire with their prey to a neighboring tree to consume it in peace.”

Encountering an adult takes some looking.

Mitch inspects a cooperative dragonfly.

Shadowdragons’ twilight timing also means their lives are less understood than more visible species. Walker observed that the nymphs often live in water 10 feet deep, near rapids and waterfalls, which help keep the water oxygenated.

Because shadowdragons hunt at dusk, they are particularly good at eating mosquitoes. That makes them a friend in my book.

Sign of a healthy river

Pygmy Snaketail (Ophiogomphus howei)

Between four total sites, the researchers turned up at least 19 species of dragonflies. Some were common, like baskettails, while others were exciting even to the seasoned hunters.

They said this diverse bounty was a testament to the health of the St. Croix.

The river’s clean and protected waters are critically important for such delicate dragonflies. In other rivers the researchers have surveyed, only some of the needed qualities are present: The Mississippi has the gravel and rocks that dragonflies like, but the water isn’t as clean. The Crow, where Curt lives, has a muddy bottom not good for many species.

The St. Croix is just right. Its clean water is thanks to the forested region that drains into it, the protections of a National Park and Wild and Scenic River, low population density in the headwaters, and a lot of stewardship.

“The watershed is everything,” Curt says.

For example, Stygian Shadowdragon nymphs live only in oxygen-rich waters (as well as several other species we saw that day). The rapids and riffles common to this part of the St. Croix are great at mixing oxygen into the water..

A low amount of algae in the water, thanks to the undeveloped landscape, can also be critical for keeping oxygen levels high.

St. Croix snaketail’s cautionary tale

Midland Clubtail (Gomphurus fraternus)

The St. Croix Snaketail is a good example of how hard it is to keep water clean enough for dragonflies. The species only lives in streams with fast flow, clean water, and rock, sand, and gravel bottoms, in largely forested watersheds.

Its specific habitat requirements make it hard to find a suitable home, but the upper St. Croix is ideal.

The dragonfly was first found in 1990 at Sunrise Landing, a little ways downstream of where we were looking. It was later found in a few other rivers in Wisconsin — and in Virginia.

The scattered nature suggests it was once common in similar streams between Minnesota and the East Coast. But by the time biologists came looking, the insect was probably already gone from rivers that had been heavily affected by humans.

Only in wild waters like the St. Croix did they hang on.

Today, the St. Croix Snaketail is listed as Endangered by the state of Wisconsin, and Threatened in Minnesota. In the few places where it lives, its numbers are low. Based on its rarity and sensitivity, the state of Minnesota upgraded its protected status in 2013.

Learning what species live where can have real impacts on supporting their survival.

Creek critters

Ron inspecting his net after swooping it through Stevens Creek.

Our last survey site for the day was the final few hundred feet of Stevens Creek, back at the landing where we started. It was lush along the little stream, ferns sprouting from the steep banks, making it feel a little like the Jurassic Period.

We didn’t see any two-foot dragonflies, but we did turn up some neat creatures.

The scientists swooped nets along the stream bed, and then picked through mud and detritus looking for nymphs. The highlight was a Fawn Darner, which likes these types of forested streams.

Curt pointed out that the Fawn Darner’s late-stage larvae was at least three years old. They are highly sensitive to water quality.

“One pollution event in those three years and they are gone,” he said. In a little creek like the ones it lives in, it wouldn’t take much to wipe out their habitat.

The fact all these species can still be found here is a testament to the power of past stewardship, and our obligation to continue protecting the St. Croix and other rivers — for ourselves, our children, and for the unique wildlife that call it home.

Thank you to Mitch, Curt, and Ron for all their help with this article, including identifying species in photos and ensuring my accuracy. Visit the Minnesota Dragonfly Society’s website for more information about that great organization!

List of observed and identified species:

A clubtail crawls away from its exuvia.
  1. Arrow Clubtail nymph (Stylurus spiniceps)
  2. Cobra Clubtail (Gomphurus vastus)
  3. Common Baskettail (Epitheca cynosure)
  4. Fawn Darner (Boyeria vinosa)
  5. Green-faced Clubtail (Hylogomphus viridifrons)
  6. Midland Clubtail (Gomphurus fraternus)
  7. Pygmy Snaketail (Ohiogomphus howei)
  8. Rapids Clubtail (Gomphus quadricolor)
  9. River Jewelwing (Calopteryx aequabilis)
  10. Rusty Snaketail (Ophiogomphus rupinsulensis)
  11. Shaddow Darner (Aeshna umbrosa)
  12. Skillet Clubtail (Gomphurus ventricosus)
  13. Splendid Clubtail (Gomphurus lineatifrons)
  14. Springtime Darner (Bsiaeschna janata)
  15. Stygian Shaddowdragon (Neurocordulia yamaskanensis)


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Dragonflies go through marvelous metamorphosis along the St. Croix River