darkly colored dragonfly with green head in flight
Door Co., WI Hine's Emerald Dragonfly © Josh Merrill Photography

Stories in Wisconsin

Rare Dragonfly Gets a Helping Hand

Lab-raised Hine’s emerald larvae released in Door County.

Julia Richards Freelance Writer

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In May, Mike Grimm drove up to Mud Lake State Wildlife Area in Door County, walked into the wetland and, in collaboration with the Wisconsin Department of Natural Resources, released 11 Hine's emerald dragonfly larvae into the shallow rivulets of water flowing amid the sedges and cattails. With any luck, by mid-June the larvae emerged as adults, with the striking green eyes emblematic of the federally endangered species.

The release was just the latest step in decades of research and conservation work since the dragonfly, once believed to be extinct, was rediscovered in 1987 at The Nature Conservancy’s (TNC) Mink River Preserve in Door County. TNC is protecting groundwater recharge areas important to the dragonfly’s larvae, which may be the key to the species’ survival.

Young woman wearing a backpack and ball cap leans over to look into a wetland with a lot of standing water with sedges
Mink River Preserve The Hine’s emerald dragonfly, believed to be extinct, was rediscovered in 1987 at The Nature Conservancy’s Mink River Preserve in Door County, Wisconsin. © Mark Godfrey/TNC

Releasing Dragonfly Larvae

Grimm, a TNC conservation ecologist based in Sturgeon Bay, had received the cooler labeled “Live dragonfly larvae—Handle With Care” earlier that day. It was sent by Dr. Dan Soluk, a biology professor at the University of South Dakota, who has studied the dragonfly for more than two decades and runs a captive rearing program.

This video shows the release of larvae at another site in Illinois where Soluk and his students also study Hine’s emeralds. Normally Soluk would bring the larvae back to his study sites himself and release them once they emerged as adults, but with COVID-19 travel restrictions, he wasn't sure he'd be able to get there in time.

Very few Hine’s emerald dragonfly eggs survive in the wild. So, the hope is that giving the animal a head start by allowing its larvae to mature in Soluk’s lab and then transplanting them into their preferred wetland habitat will help more of them survive to adulthood and expand the population in Door County.

Green-eyed dragonfly being carefully held between two fingers of a person’s hand
Hine's Emerald Dragonfly Dr. Dan Soluk has studied the dragonfly for more than two decades; here one of his students holds a Hine’s that has been tagged as part of one of his habitat research studies.

Importance of Door County for Hine's Emerald Dragonflies

Soluk's partnership with TNC in Wisconsin is just one example of how TNC both facilitates scientific study and uses the findings to inform its work.

“The Hine's emerald plays a big part in our work here in Door County,” Grimm says. “Because it depends on clean groundwater to survive, we’re protecting the groundwater flowing towards the wetlands it utilizes. We also consider the presence of this endangered species whenever we plan management work in the wetlands where it lives.”

TNC owns a little over 4,700 acres in Door County, split between four different preserves, all of which are home to Hine's emeralds. Door County hosts, in fact, the greatest abundance of this endangered dragonfly in the world.

Door County Preserves Where Hine's Emerald Occurs

Prior to the species’ rediscovery, little was known about the 2.5-inch-long insect. But Soluk and his students are changing that.

Soluk's research base is a TNC cabin at Mink River Preserve. Having this facility for his students to use during the summer makes the research possible, he says. “One of the most difficult things when you're doing science at remote locations is the cost of accommodations.”

Photo of a human hand with one finger pointing to a small hole in the mud with sprigs of green grass growing up
Crayfish Burrow Hine’s emerald dragonfly larvae survive dry periods and winter by hiding in crayfish burrows.

Into the Predator's Lair

The Hine's preferred habitat is groundwater-fed wetlands over dolomite or limestone bedrock, creating slightly alkaline water. Their maturation process from egg to dragonfly lasts four to five years, much longer than that of most dragonfly species, and is one of the reasons the species is endangered.

The dragonfly also occupies a unique niche, adapted to survive long periods in dry conditions, as the spring-fed streamlets in these wetlands dry up each summer. Hine's emerald larvae reserve their energy stores through the dry periods, as well as the winter, by hiding out in crayfish burrows, Soluk explains.

It would seem an unlikely solution, seeing as crayfish are known to prey upon the larvae. “You basically have an animal that you want to conserve that requires the presence of one of its predators,” Soluk says.

“[It's] a really interesting way to understand how ecosystems work...” he says. “If we want to maintain their integrity, we've got to think about, not just the simple needs that we might envision for the species, but the complicated interactions that are occurring on many levels.”

It's still not known exactly how enough Hine's larvae avoid being eaten in the burrows. One theory, studied by one of Soluk’s grad students, is that the dragonfly’s hairiness, which likely helps it conserve water, also collects material such as feces, perhaps disguising its scent.

Eleven metal rods with red flags are planted throughout out a wetland with a few small scattered conifer trees
Hine's Habitat Eleven Hine’s emerald larvae were released into the shallow rivulets of water flowing amid the sedges and cattails wetland at Mud Lake State Wildlife Area in Door County.

The Hine's emerald plays a big part in our work here in Door County. Because it depends on clean groundwater to survive, we’re protecting the groundwater flowing towards the wetlands it utilizes.

TNC Conservation Ecologist

Threats to the Hine's Emerald Dragonfly

Among the major threats to the Hine's emerald are groundwater contamination and depletion, especially from nearby development. “When you have a wetland area, it's important to protect not only that wetland but those areas that provide groundwater to the wetland. And that can be a big area,” Soluk says.

Bringing attention to the species is a way to get people thinking about the larger systems that they—and we—need to survive. “I think people can relate to an animal better than to the hydrology of groundwater movement,” Grimm says. Besides providing crucial habitat for the Hine's, he explains, TNC works with area stakeholders to protect groundwater resources, which also provide well water for people.

Man in ball cap and brown jacket bends over in a wetland to look at the vegetation.
North Bay-Mud Lake Preserve TNC Conservation Ecologist Mike Grimm at North Bay-Mud Lake Preserve in an area that Hine’s emeralds use for feeding and possible breeding in the smaller rivulets of water that feed this stream. © Mark Godfrey/TNC

With regulatory protections on the decline both at the state and national level, it's more important than ever for conservation groups like TNC to protect unique habitats, like groundwater-fed wetlands.

“If you look at an adult Hine's emerald, it's a beautiful creature that has been around for maybe a million years. And its relatives have been around for 300 million years,” Soluk says. This species has intrinsic value worthy of protection, he says. And in understanding and protecting what this unique species needs to survive, we also protect the water we need for our own survival.

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Julia Richards is a freelance writer.