Diminutive Dragonfly Makes New Appearance in Michigan
By Ed Ricciuti
When David A. Marvin headed to riverbank to photograph dragonflies one pleasant May day three years ago, he found one, all right, a real shocker. He could hardly believe his eyes. It was a minim of a dragonfly, Ophiogomphus howei, sometimes called a pygmy snaketail, which turned out to represent a new population of this rare species, far from the two previously known populations and in a habitat sufficiently different that scientists may revise their thinking about the environmental conditions it requires.
“We may need to reconsider our assumptions that this is a sensitive species strongly tied to pristine environments—or, alternatively, it is more widely distributed than we think, but it’s reputation as mysterious and elusive is really well-deserved,” says Julie Craves, who, with her engineer husband Darrin O’Brien, runs the Michigan Odonata Survey.
The couple, along with Marvin, are authors of a paper describing the new population in the Journal of Insect Science. Marvin snapped the photo of the dragonfly in the Riverbend Natural Area, a preserve owed by Ingham County in the town of Delhi, a few miles south of Michigan’s capitol, Lansing. Subsequent searches along the river over the next couple of years turned up a more snaketails, a handful but enough to represent a new population of these inch-long insects. As well, a homeowner who is a dragonfly buff photographed a dead snaketail on the floor of his home a few miles downstream of the natural area in Eaton County, further extending the range of the population.
Until Marvin’s camera lens captured his snaketail, the species was known from two widely separated regions, far from the Grand River, which flows 252 miles across southern Michigan into Lake Michigan. (The city of Grand Rapids is situated near its mouth.) One area inhabited by the species spans the northern half of Wisconsin, edging into Minnesota and a tad into Michigan’s Upper Peninsula. An eastern population coincides with the Appalachians, from New Brunswick to South Carolina, west to Kentucky. Almost 400 kilometers separates the nearest group of O. howei from the new population. The populations are not continuous, but exist in scattershot fashion, sprinkled through forested areas on clear streams and rivers, of high water quality and fast flow, often with rocky or gravelly substrates. The forest environment that includes population centers of O. howei is relatively undisturbed with little agriculture, according to the authors.
All of which makes the Grand River population something of a departure from the norm. While the Grand River’s banks are relatively woody, with considerable floodplain forest, where the new population was found, it is far from pristine. “Polluted is kind of a strong word,” says Craves, but “it’s often silty, and more serious problems with pollution occur up and downstream in the more urban locations. How much of the upstream inputs translate into specific problems at this location probably depends a lot on periodic discharges and rainfall. The primary issues for this stretch of the river, we surmise, are probably sedimentation and excess nutrients or pesticides from agriculture.” There is considerable agriculture in the locale, which as well lies within the Lansing-East Lansing metropolitan area, which has a human population of more than a half million. Besides a high dose of pollutants from nitrogen fertilizers, pollutants found in the river as a while include mercury and polychlorinated biphenyl (PCB).
The authors verified the new population by successfully searching for O. howei, which has a flight season in late spring, in its various life stages, including exuviae, the exoskeletal skin shed by aquatic larvae as they emerge into aerial adulthood. Braving hordes of spring-active mosquitoes, which the snaketails eat, and more than a few ticks, they found enough specimens to verify their discovery.
“We are optimistic that the observations of at least 10 adults reported here from a limited number of surveys over several years could indicate a robust population at the southern Michigan site,” say the authors. The population is important because, due to its limited range and habitat requirements, species such as O. howei, listed as “threatened” in Michigan, tend to be at risk.
The discovery of the new population is unusual in that none of the authors is an academically trained, professional entomologist. Craves, who describes herself as an ecologist, has a bachelor’s degree in environmental studies and is retired founder and director of the Rouge River Bird Observatory at the University of Michigan-Dearborn. However, she is on the board of the Michigan Entomological Society and an associate editor of its journal. O’Brien is an aerospace engineer and Marvin, who was a political science major, is a nature photographer and an employee of the Michigan Liquor Control Commission.
Journal of Insect Science
Ed Ricciuti is a journalist, author, and naturalist who has been writing for more than a half century. His latest book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His assignments have taken him around the world. He specializes in nature, science, conservation issues, and law enforcement. A former curator at the New York Zoological Society, and now at the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.