Riverbend Park Dragonfly Study Report: February 2005
by Karen Sheffield
Life long predators, dragonflies spend most of their life as a larva in aquatic habitats before emerging into the winged adult insect. Many species are habitat specific and require unpolluted aquatic environments to survive, such as seeps, streams, and ponds. Dragonflies are valuable indicators of the general ecosystem health: "the presence of a vigorous and diverse odonate (dragonfly and damselfly) fauna will always be a reliable indicator of the stability, health and integrity of a wetland ecosystem."¹
Riverbend Park hosts a variety of wetland and meadow habitats that attract dragonflies. Thirty-four dragonfly species have been recorded to date, of which 30% of the dragonflies are state rare or watch listed species. (See Table 1*) Riverbend is home to more than 10% of the dragonfly species in the whole of North America.
Several great records were made this past season. The Spine-crowned clubtail, a hybrid G3G4 and state rare species, had historically been recorded from only two locations along the Potomac River. For the first time in 25 years the Spine-crowned clubtail was documented along the Potomac at Riverbend Park, also making this the first record in Fairfax County.
The Midland clubtail (S1-state rare) and Ocellated darner (S3 - watch listed) were documented this season as well. The Cyrano darner (S3 - watch listed) breeds in Carper's Pond, a wooded pond that is formed from a seep within the park.
Five cast skins of a clubtail species have proven difficult to identify. The species is either the Elusive clubtail (G3 - globally rare, S1 - state rare) or the Russet-tipped clubtail (S3 - watch listed). More study is required on these.
The past four years have focused on studying ponds, a vernal pool and a portion of the Potomac River. Seeps and park streams remain to be studied in coming years. These environments are favorable to specific dragonflies, many of which are state listed. This will be the focus of the 2005 study.
Much thanks goes out to all of our volunteers and staff and to Richard Orr who has verified several challenging adult species and cast skins (exoskeletons). Volunteers: Edward Chein, Ryan Meczkowski, Naghma Malik, Lydia Lanni, Ellie Clark, Kit Sheffield, Andrea Menzo, Lynn Mobley, Riverbend Dragonfly Survey Group, Marijke Gate, Jamie Fish, John Callow.
¹Corbet, P.S. (1999) Dragonflies: Behavior and Ecology of Odonata, p204.