The Dragonfly Society of the Americas species of the month is the Hine’s Emerald dragonfly (Somatochlora hineana), part of the Corduliidae or Emerald family. Dennis Paulson, author of Dragonflies and Damselflies of the East, notes this species is 58-63 mm long (just under two-and-a-half inches), with a flight time of June-August within its range, which is restricted mainly to the Midwest. The Hine’s Emerald dragonfly’s preferred habitat, he writes, is an area with a spring and dolomite underlay, often associated with fens. It is the only dragonfly on the United States Endangered Species List. Join dragonfly chaser Cindy Crosby as she learns more about the efforts to ensure the survival of this unusual species.
Hine’s Emerald Dragonfly (Somatochlora hineana), Door County, WI. July 2012 (Copyright Dan Jackson)
Growing Up Endangered
Some people want to hear Bob Dylan in concert before they die. Since I began chasing dragonflies in 2005, I’ve wanted to see a Hine’s Emerald dragonfly in the wild. For more than a decade and a half, they eluded me. And then… .
Urban Stream Research Center, Blackwell Forest Preserve, Warrenville, IL. March 18, 2024. (Copyright Cindy Crosby)
Snow is falling as I pull up to the Urban Stream Research Center in Warrenville, IL, located in DuPage County, Illinois’ Blackwell Forest Preserve. I push a buzzer, and Aquatic Resources Supervisor Andres Ortega opens the locked doors and greets me with a smile. It’s been several years since I’ve visited the center, and I’m eager to see what’s changed. Ortega ushers me past posters about mussels and fish to where the real action is happening in the back.
Here, the federally endangered Hine’s Emerald dragonflies are waiting for me. Hundreds of them. But unrecognizable as such to most people. The center is a captive rearing facility, where dragonfly nymphs live until they can be released into good local habitat.
Hine’s Emerald dragonfly (Somatochlora hineana) nymphs in two sizes, Urban Stream Research Center, Blackwell Forest Preserve, Warrenville, IL. March 18, 2024 (Copyright Cindy Crosby)
Along the back wall, large industrial refrigerators hold trays of dragonflies in both nymph and egg stages, housed in small sample cups (think about your last urinalysis, and you’ll know the cup). The process of obtaining these dragonflies is laborious. Ortega tells me that University of South Dakota staff go out in June and July to capture females flying along the Des Plaines River watershed, just outside Chicago. Female Hine’s Emerald dragonflies, he tells me, come to sexual maturity quickly after emergence, and have a good chance of being mated and ready to lay eggs when captured. Once in hand, the scientist taps the female’s abdominal tip into the sample cup of water, which prompts her to release her eggs.
Hine’s Emerald dragonfly (Somatochlora hineana) eggs, Urban Stream Research Center, Blackwell Forest Preserve, Warrenville, IL. March 18, 2024. (Copyright Cindy Crosby)
These eggs, about 100 average in each ovipositing sample, went to Dr. Daniel Soluk’s laboratory at the University of South Dakota, where the Hine’s Emerald is extensively studied. In October, they were redistributed to three receiving centers, including the Urban Stream Research Center here. Some years, Ortega says, the center may receive more than a thousand eggs; other years, like 2023, a drought year in the Midwest, the number may be as little as 300.
Aquatic Resources Supervisor Andres Ortega checks a sample cup of Hine’s Emerald dragonfly nymphs (Somatochlora hineana), Urban Stream Research Center, Blackwell Forest Preserve, Warrenville, IL. March 18, 2024 (Copyright Cindy Crosby)
Through the winter, cups of eggs are refrigerated at temperatures around 40 degrees Fahrenheit, in the dark. In the spring, Ortega will float the cups in special water tanks in which the water is gradually warmed, to hatch the eggs. However, egg hatch can happen as early as January, he tells me, so he and his associates will check the refrigerator about once a week to see how the eggs are progressing. It’s tricky, he notes, as the more he checks them, the more they are exposed to light and warmth, which may trigger a hatch.
Hine’s Emerald dragonfly nymph (Somatochlora hineana), Urban Stream Research Center, Blackwell Forest Preserve, Warrenville, IL. March 18, 2024 (Copyright Cindy Crosby)
The eggs and eventually, the nymphs are carefully segregated into groups from specific areas, as Ortega said the genetics of each region are specific enough that they want to keep that integrity intact. Once hatched, they are next moved to rearing cups where very young nymphs are fed a diet of microworms, and older nymphs are fed wild-caught zooplankton (mostly copepods, Ortega said).
Hine’s Emerald dragonfly nymphs (Somatochlora hineana), Urban Stream Research Center, Blackwell Forest Preserve, Warrenville, IL. March 18, 2024 (Copyright Cindy Crosby)
Later, as the nymphs move through instars toward maturity, they’ll be placed into large raceway tanks during the growing season. When in the tanks, they’ll roam in 65 degree Fahrenheit water and feed on isopods (think aquatic “roly polys”).
Hine’s Emerald dragonfly (Somatochlora hineana) tanks, Urban Stream Research Center, Blackwell Forest Preserve, Warrenville, IL. March 18, 2024 (Copyright Cindy Crosby)
In November, the water will be gradually cooled and eventually, the nymphs moved back into the refrigerators. There, they will live in their diapause state until late winter or early spring, when the process is repeated.
The majority of the dragonfly nymphs will reach maturity after about three years of growth under laboratory conditions, Ortega said, adding that in the wild, this may take four to five years. When they near their final instar, they may be taken to areas like Waterfall Glen Forest Preserve in Lemont, IL. There, under the supervision of University of South Dakota researchers, they are placed in a mesh laundry basket with its bottom submerged two inches deep in a children’s blue wading pool. The nymphs will be monitored until emergence, when they are released from the laundry basket to take to the skies in June and July. There, they will delight—and elude—dragonfly chasers like myself.
Hine’s Emerald Dragonfly (Somatochlora hineana), Door County, WI. July 2012 (Copyright Dan Jackson)
I thank Ortega for the tour, and return to my car. Snow continues to fall. I think back to a hot day in July of 2023, when I went out with Marla Garrison and fellow dragonfly chaser Joyce Gibbons to a local forest preserve noted for hosting the Hine’s Emerald dragonfly.
Cook County Forest Preserve, IL. July 10, 2023. (Copyright Cindy Crosby)
We had tramped through head-high cattails and grasses, with water squishing underfoot. Garrison put on her big shiny sunglasses (which seem to attract Emerald family males) and we crossed our fingers. And then… .
Hine’s Emerald dragonfly (Somatochlora hineana), Cook County Forest Preserve, IL. July 10, 2023. (Copyright Cindy Crosby)
“Look!” It was the unmistakable patrolling silhouette of a Hine’s Emerald dragonfly. And—another. And—was that another?
Hine’s Emerald dragonfly (Somatochlora hineana), Winnebago County Forest Preserve, IL. June 19, 2021. (Copyright Joyce Gibbons.)
Now, I can die happy. Eat your heart out, Bob Dylan fans! I’ve seen something better—-the adult Hine’s Emerald dragonfly in flight. And it was worth the wait.
Cindy Crosby is the editor of the DSA’s Species of the Month blog, which began in July of 2021. She is the author or contributor to more than 20 books, including Chasing Dragonflies: A Natural, Cultural, and Personal History (Northwestern University Press, 2016). She works with volunteer teams to document dragonflies at The Morton Arboretum in Lisle, IL, and Nachusa Grasslands in Franklin Grove, IL. When she’s not writing or giving natural history programs, you can find her working in her garden in Glen Ellyn, IL.
Special thanks to Dan Jackson, who contributed his beautiful photos of the adult Hine’s Emerald dragonfly for this blog post.
