May Species of the Month: Blue Dasher (Pachydiplax longipennis)
Male Blue Dasher dragonfly (Pachydiplax longipennis), Schulenberg Prairie, Lisle, IL (undated).
Our May DSA species of the month is the Blue Dasher dragonfly (Pachydiplax longipennis) in the skimmer family Libellulidae. It’s the only member of its genus. Ode expert Dennis Paulson notes the size is variable; with a range of 28-45 mm (one to 1.7 inches); and is often abundant where it’s found. Look for it in ponds and lakes in most of the central to eastern United States, north to Canada and south into Mexico. Join dragonfly chaser and DSA blog coordinator Cindy Crosby as her blue dasher dragonfly encounters lead to a face-off with a bigger species.
Adventures in Dragonfly chasing
Mama bison isn’t happy. And if mama bison ain’t happy… .
Bison (Bison bison), Nachusa Grasslands, Franklin Grove, IL. (2021)
I’m standing knee deep in a pond where I’ve fled with my binoculars, camera, net and clipboard. Just moments ago at Nachusa Grasslands in Franklin Grove, IL—90 miles west of Chicago—I was strolling along the shoreline, making hash marks on my data sheet. I’m one of a dozen or so citizen scientists here who volunteer to identify and count dragonflies and damselflies from March-October; just another way to measure the health of our wetlands, streams, and ponds. It is also a way to add data to the state of Illinois’ repository of insect information. This pond is full of the typical dragonfly species found in Illinois.
Pond at Nachusa Grasslands, Franklin Grove, IL. (2017)
Twelve-spotted skimmers. Eastern amberwings. Common white-tails. And then, there are the blue dashers. They are a common sight in the Illinois prairies and ponds I often hike, and I can count on tallying numerous individuals in the summer. Very predictable. Not too exciting.
Male Blue Dasher dragonfly (Pachydiplax longipennis), The Morton Arboretum, Lisle, IL. (2021)
Occasionally, an unusual dragonfly will show up. I have had a single sighting of the four-spotted skimmer at this Nature Conservancy preserve. It’s only one of two times I’ve seen it in my more than 17 years of dragonfly monitoring.
Four-spotted skimmer dragonfly (Libellula quadrimaculata), Schulenberg Prairie, The Morton Arboretum, Lisle, IL. (2021)
So, I hike and patiently count the usual ode suspects. Widow skimmer. Eastern amberwing. Twelve-spotted skimmer. Twelve-spotted skimmer. Another twelve-spotted skimmer. Then, I add hash marks for each blue dasher to my data sheet—so many blue dashers!---while alert for anything flying or perched that looks unusual. Who knows what might show up? I’m hoping for something exciting. Sometimes blue dasher dragonfly counting is a little monotonous.
Be careful what you wish for! Nachusa has a herd of about 125 bison, the first brought here in 2014 as part of an effort to restore tallgrass prairie. Illinois is known as “the prairie state,” but much of the prairie here — including the prairie wetlands—has been lost to agriculture and development. Many prairies were drained by farmers to make the wetlands dry enough to plow.
Of the approximately 22 million acres that once blanketed Illinois, only about 2,300 original prairie acres remain. The adult male bison who roam Nachusa Grasslands can weigh up to 2,000 lbs; female bison about half that much. Heavy? Yes. And also fast. Bison can run up to 40 miles per hour.
Regal Fritillary Butterfly (Speyeria idalia), Nachusa Grasslands, Franklin Grove, IL. (2021)
With the loss of that vast grasslands and its associated ephemeral ponds and streams came the loss of odonata habitat. I’m grateful to have almost 4,000 remnant or restored prairie acres to explore with other monitors, and to have the opportunity to observe what dragonflies and damselflies visit and reproduce here. Blue dashers may be plentiful, but they are also fun to watch. After mating, blue dasher males hover guard the females (flying circles around them above the water) while the females oviposit by tapping their abdomen tips into the water. I often see the males perched at even intervals along the shoreline.
Today, however, lulled into daydreaming as I counted familiar dragonflies, I’ve goofed. I’m usually on high alert for the presence of bison. So I’m dismayed when I cross a small hill close to the pond and there they are. A mama bison with her baby.
Bison (Bison bison) calf, Nachusa Grasslands, Franklin Grove, IL.
Mama bison are very protective of their calves and this one is no exception. Her head jerks up as I pop into view and her eyes meet mine. Uh, oh. I quickly backtrack toward the pond, hoping she’ll return to grazing. No luck. Here she comes, over the rise. Stumbling through the tallgrass, I wade into the pond, trying to blend in with the reeds and cattails. Slurp. Slurp. My knee-high rubber boots have never moved through the muddy pond bottom so fast. I look over my shoulder and stand still. Bison have notoriously bad eyesight, so my lack of motion should cause her to lose interest. She stands on the hill and looks in my direction for what seems like hours, but in reality, was only minutes. Long minutes. Then, shaking her head, she turns and moves back over the hill.
My legs are wobbly as I retrace my path back to my car. One of the reasons I love chasing dragonflies is the encounters with other creatures I see along the way. Birds. Butterflies. Blue dasher dragonflies.
Female Blue Dasher dragonfly (Pachydiplax longipennis), Belmont Prairie, Downers Grove, IL (2016).
This bison encounter, however, will hopefully be my last up-close-and-personal one. I’ll never call counting blue dasher dragonflies boring again.
Cindy Crosby is a volunteer dragonfly steward who coordinates two teams of about a dozen monitors each; one team at Nachusa Grasslands in Franklin Grove, IL, a Nature Conservancy site, and another at The Morton Arboretum in Lisle, IL. She is the author of Chasing Dragonflies: A Natural, Cultural, and Personal History (Northwestern University Press), Tallgrass Conversations: In Search of the Prairie Spirit (Ice Cube Press) and The Tallgrass Prairie: An Introduction (Northwestern University Press). Cindy coordinates the DSA “Species of the Month” blog and loves to garden, hike and bake. She is also a prairie steward who blogs each week about dragonflies, prairie, and gardening at “Tuesdays in the Tallgrass at Wordpress.” Her natural history classes and programs are found at www.cindycrosby.com.
