Aeshna sitchensis Hagen, 1861
Basis for Listing
The Zigzag Darner (Aeshna sitchensis) is a boreal species that occurs in Canada and parts of the northern United States, and Minnesota lies along the southern edge of its range. Single specimens or very small populations have been confirmed in only six northern counties: Lake and Cook in the Northern Superior Uplands Section, and Roseau, Lake of the Woods, Beltrami, and Koochiching in the Northern Minnesota and Ontario Peatlands Section (Odonata Central 2017). This species relies on cool water habitats in bogs and fens for breeding. Based on the very specific habitat needs of the Zigzag Darner and the few isolated populations encountered in Minnesota, it was listed as a species of special concern in 2013.
Wisconsin has also listed the Zigzag Darner as a species of special concern.
Averaging 6 cm (2.4 in.) in length, the Zigzag Darner is the smallest of Minnesota’s nine species of “mosaic darners” (genus Aeshna) and readily identified by the thin, sometimes broken, thoracic side stripes that are sharply bent into zigzags. The abdomen of the male is strongly marked with blue, the female's abdomen slightly less so. Male claspers (upper terminal appendages) are paddle-shaped. The species is more likely to perch on the ground than others in the genus (Paulson 2009).
Zigzag Darners prefer sedge and moss dominated northern poor fens and small (< 8.4 m² [10 sq. yds.]) cold northern open bogs in acidic peatland systems. Although normally wet throughout the year, these habitats may dry out temporarily in times of drought (Walker 1958).
Biology / Life History
The flight period of the Zigzag Darner is from early June to late September. Males are less likely to fly regular territorial patrols than others of the genus. Both sexes fly low to the ground or water, keeping at or below the tops of sedges. Females oviposit in a variety of substrates from open water at the base of sedges or grasses to moss at the water’s edge as well as on algal mats or mats of decaying vegetation. The Zigzag Darner stops feeding earlier in the day than most of the Aeshna species; it does not feed at dusk, as do the others. (Dunkle 2000, Paulson 2009). Very little is known about this species' larval life cycles or habits.
Conservation / Management
Although the peatland breeding habitats needed by the Zigzag Darner tend to be currently inaccessible and remote, there has been some recent activity hinting toward a renewed interest in peat mining in Minnesota. Such activity could severely threaten the survival of this species in mining areas. The breeding habitat is susceptible to degradation by any land use activity that changes the hydrology of the habitat or increases erosion or run-off.
It is assumed that global climate change will move the southern edge of the boreal biome to the north. This change could eliminate Zigzag Darners from the state.
Conservation Efforts in Minnesota
The designation of Red Lake Peatland, Mulligan Lake Peatland, and Sand Lake Peatland as state Scientific and Natural Areas will play a large role in the conservation of this species. The non-profit Minnesota Dragonfly Society is looking for the Zigzag Darner (among many other species of Odonata) throughout Minnesota through surveys and educational workshops. These surveys are conducted by volunteers and are supported through an Enbridge Ecofootprint Grant through 2018.
Kurt Mead (MNDNR), 2018
(Note: all content ©MNDNR)
References and Additional Information
Abbott, J. C. 2006-2017. Odonata Central: An online resource for the distribution and identification of Odonata [web application]. <http://www.odonatacentral.org>. Accessed 21 March 2017.
Dunkle, S. 2000. Dragonflies through binoculars: a field guide to dragonflies of North America. Oxford University Press, New York, New York. 266 pp.
Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.
Paulson, D. 2009. Dragonflies and damselflies of the west (Princeton field guides). Princeton University Press, Princeton, New Jersey. 536 pp.
Walker, E. M. 1958. The Odonata of Canada and Alaska : Anisoptera. Volume 2. University of Toronto Press, Toronta, Ontario, Canada. 330 pp.