11 July 2023

Plains Emerald -- new for Michigan

Update: Our article on this new additions has been published in Argia, a publication of the Dragonfly Society of the Americas. You can read the paper here.

Plains Emerald (Somatochlora ensigera) is found primarily west of the Mississippi River. Eastern records come from three U.S. states (Wisconsin, Indiana, and Ohio) and one Canadian province (Ontario, although there are multiple records from western Ontario and provinces further west). There are no previous Michigan records.

As part of our efforts to document the distribution of Michigan Odonata, the Michigan Department of Environment, Great Lakes, and Energy (EGLE; formerly the Department of Environmental Quality) has been sending us nymphs collected during their watershed surveys. These surveys only identify aquatic macroinvertebrates to family, so Darrin has been spending winter days identifying as many to species as possible, and we've garnered many new county-level records form these efforts. 

Several nymphs collected by EGLE's Elizabeth Stieber in August 2022 in southern Menominee County in the western Upper Peninsula were highly suggestive of Plains Emerald. Many traits, particularly measurements and ratios, were difficult to discern on these early to mid-instar individuals, so we didn't want to make a definitive call on ID. 

The nymphs went next to Anthony Cognato and Jordy Hernandez at Michigan State University for DNA sequencing as part of a larger project on Somatochlora phylogeny. Two of the nymphs were a match for Plains Emerald, based on reference material from Minnesota. DNA could not be sequenced from a third nymph. 

The two matching nymphs were from the Little River southeast of the town of Wallace, ~8 km east of the Wisconsin border. The third nymph was from Kelley Creek, northwest of the town of Birch Creek and ~5.5 km east of the Wisconsin border. The closest record of Plains Emerald to these Michigan locations is from 1988 in neighboring Marinette County, Wisconsin.

Collection site of two Plains Emerald nymphs on the Little River, Menominee County, Michigan
Photo by Elizabeth Stieber.

This brings the Michigan checklist to 170 species based on voucher specimens.

Further reading:

Beckemeyer, R. 1998. A brief history of the Plains Emerald - Somatochlora ensigera. Argia 10:17–20.

DuBois, R. B., and K. J. Tennessen. 2008. Nymphal habitat of Somatochlora ensigera Martin (Plains Emerald). Argia 20:9–11.

Williamson, E. B. 1912. The known Indiana Somatochloras (Odonata). Entomological News 23:152–155.

Williamson, E. B. 1922. Indiana Somatochloras again (Odonata, Libellulidae). Entomological News 33:200–207.