AT VIRGINIA’S Back Bay National Wildlife Refuge in in late July, a kaleidoscope of dazzling crimson, tangerine and sapphire dragonflies surround a group of visitors hiking along one of the sandy pathways. The group was enjoying the beautiful summer day watching the dragonflies as they spiraled through the air, like shards of stained glass enchanted to dance.
As the explorers trekked through the friendly swarm, invigorating ocean breezes floated through gently pushing dragonflies to higher elevations or tempting them to relax on nearby sea oats.
A female white-tailed dragonfly in Hanover, Pennsylvania. The Mid-Atlantic states used to be prime habitat for dragonflies, but over the decades, increased urbanization, non-point source pollution, and stream channelization have affected their freshwater habitats. Photo by Henry T McLin.
Established in 1938, the refuge features a unique combination of dunes, wetlands and woodlands bordered by the Atlantic Ocean creating a comfortable home to an average of 17 dragonfly species - including three rare ones. This magical scene of hundreds of dragonflies whirring through the area is common in the refuge and elsewhere in the Mid-Atlantic.
Their abundance is easy to take for granted. But while dragonflies are adaptable, they are increasingly under threat, and this beautiful insect that’s one of the prime indicators of a healthy ecosystem could potentially disappear if their habitats aren’t respected.
LONG BEFORE DRAGONFLIES put on their summer show, each of them begins their life as a tiny, cylindrical 0.5mm egg on aquatic plants or still water. After about six weeks, the insect enters its larva stage emerging from its birthplace to wander the world in a cockroach-like shell (known as exuvia) for as long as three years. It lives underwater and roams the surrounding area for bugs. It is only after finally reaching maturity that a dragonfly discards its encasing, completing its transformation into a vibrant winged creature, not unlike the journey of a butterfly. That period of vibrancy, the moment where human beings are most likely to pay any attention to dragonflies, is short lived. Once it begins to fly, a dragonfly will live no longer than two months. Many will live less than a week.
But in those few, short weeks, dragonflies have an important role to play. They’re a crucial link between aquatic and terrestrial ecosystems because of their amphibious and predatory life history, says Joe Girgente, a Texas Tech University Biological Studies Master’s student. “Their presence or absence from an area can be an indicator of both water quality and the quality of the adjacent riparian area on which they depend for successful foraging and reproduction.” Besides this, their scarcity near certain water bodies could signal that the entire aquatic community around it is suffering.
Historically, the Mid-Atlantic states are prime habitat for dragonflies. In Maryland alone, there are over 182 species of dragonfly, many of them thriving along the historic Chesapeake and Ohio canals. In Sussex County, New Jersey where around 142 species have been recorded, you’ll find the fiery reddish-orange autumn meadowhawk and the show-stopping black saddlebag which looks as if it’s carrying a dark satchel on its hind wings. One species, the spatterdock darner, flocks to regions in Maryland and Pennsylvania that host spatterdock water lilies where the dragonflies lay their eggs. The banded pennant is native to New Jersey’s ancient pine barrens. Experts say the secret behind such dragonfly diversity is likely the vast extent of wetland ecosystems in the Mid-Atlantic.
But over the decades, increased urbanization, non-point source pollution, and stream channelization have affected freshwater habitats that dragonflies need to thrive. While the edge of lower Virginia to upper New Jersey is filled with some of the largest wetlands in the country, many of these waterways have been polluted from wastewater and chemicals from surrounding industrial centers and agricultural sites.
In recent years though, dragonflies are being newly appreciated for their beauty and diversity. Dragonfly watching groups, much like birding groups, have formed to track them down and chronicle them. It has also become increasingly apparent that dragonflies are incredible bioindicators. New research has helped scientists understand water oxygen levels and cleanliness simply by how dragonflies interact with it.
From 2011 to 2016, Dr. Ami Riscassi, a research scientist at the University of Virginia, dug into stream sediment throughout the Great Smoky Mountains and Shenandoah National Parks to collect dragonfly larvae. These research efforts, which have been going on since 2009, are part of the Dragonfly Mercury Project — a United States Geological Survey and National Park Service initiative designed to help us better comprehend how dragonflies interact with methylmercury, a neurotoxin that dangerously affects both wildlife and humans.
Using dip nets to till into stream sediment, Riscassi and her fellow volunteers gathered about 15 dragonfly larvae specimens per site, froze them, and sent them to a laboratory for an analysis of body mercury content. Although dragonflies likely aren’t themselves harmed by mercury, their food sources and predators might be. By monitoring the larvae, scientists get a unique glimpse into an ecosystem’s health and how mercury from atmospheric deposition affects it. Dragonfly larvae are ideal for this purpose because they’re easy to catch and tend to live long lives so scientists can get a long-term view of things.
The effort has encouraged others to better understand how this toxic chemical is affecting waterways in our National Parks. Further research can potentially help us learn how dragonfly habitats nationwide are affected and the best ways to preserve these aquatic communities.
A green darner near near Morgantown, West Virginia. Beyond their role as indicators of a healthy ecosystem, dragonflies are also significant predators of agricultural pests. Photo by zodia81.
A Halloween pennant in Cape May, New Jersey. Photo by PhotoJeff.
A golden-winged skimmer in Frederick County, Maryland. Photo by Mike Ostrowski.
BEYOND THEIR ROLE as indicators of a healthy ecosystem, dragonflies can also fill the role of predators of agricultural pests. Margaret Hartman, a Master’s student at the University of Maryland’s Department of Entomology, spent two years studying dragonfly composition and diet on several Maryland farms. While often dismissed as inadequate agricultural biocontrol predators she found this wasn’t the case during her research. “Here in the United States we don’t usually think of them that way. There were days on a farm where I surveyed hundreds and to know they were eating and foraging was really great validation.” Their diet often consists of horseflies, mosquitoes, flies, and moths — insects that can cause severe crop damage. In fact, one dragonfly alone can munch on hundreds of mosquitoes each day helping to control their population.
But although dragonflies can be helpful insects to have on a farm, agriculural practices often decrease their populations.
“One farm in Upper Marlboro had a well-developed retention pond with a good quality vegetative border that had been there about 50 years and there was a wealth of dragonflies there,” Hartman said. “Another Clarkesville farm had huge lagoons but they pumped water from livestock fields into them and the edges were man-made with boulders and rocks so there was hardly any emergent vegetation.”
Even small changes in land being used for agricultural sites can have a big impact on dragonfly health. By simply adding or leaving emergent vegetation around retention ponds and lagoons, it can create a welcoming place for dragonflies which in return could lead to eco-friendly farm pest control.
Monoculture farms, however, will never be a prime habitat for dragonflies. Everywhere, dragonflies are losing wetlands that form the basis of their habitat. Perhaps one of the most significant issues is the constant development in delicate watershed areas that often results in streams and rivers being artificially shrunk or drained.
“If you took satellite photos of the country, you’d see the expansion of urban areas which destroys habitats,” said Dr. Harold White, an emeritus professor of chemistry and biochemistry at the University of Delaware and a devoted dragonfly researcher. “These human-caused changes of the physical environment are critical.”
There is, however, hope for the dragonflies. Idylwild Wildlife Management Area in Caroline County, Maryland is an example of this.
Walking through its landscape today, you’d have no idea that the park was once a major sand and gravel mine. Run by the Seaford Sand & Gravel Company, the operation ran from the 1960s until the 1980s. In 1995, plans began for it to be reversed back into a natural area, including by flooding the abandoned pits to make wetlands and ponds. Slowly, wildlife returned and the land now hosts over 84 dragonfly species, including the elusive arrowhead spiketail and Selys’ sundragon.
“This habitat didn’t exist 60 years ago and it’s not natural, but it has created little microhabitats that are colonized by dragonflies not easily found elsewhere,” White says.
To prevent a collapse of dragonfly populations across the Mid-Atlantic, these changes will need to occur on a broader scale. While dragonflies can adjust to changes, there may come a point where the scale has tipped too far, and there aren’t viable habitats for them to survive. A 2021 study by the International Union for Conservation of Nature found that 16 percent of 6,016 dragonfly species could be at risk of extinction as wetlands vanish across the globe. This includes the brook snaketail (found mostly in New Jersey) which is quite sensitive to watershed changes and has been listed as a species of concern in the state.
There are untold questions about our environment that dragonflies could help us answer if we take the time to listen to one of the world’s oldest insects. “Dragonflies have stood the test of time,” Hartman said. “We need to expand what we expect of them.”
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