Little Forks Conservancy macroinvertebrate samples provide useful data to michigan odonata survey

Last month, MSU Adjunct Curators and husband and wife duo, Darrien O'Brien and Julie Craves, examined Little Forks Conservancy's previous years' macroinvertebrate samples. Specifically, they were looking to identify macroinvertebrates of the genus Odonata, or as they are more commonly called, Dragonflies and Damselflies. These samples helped to fill data gaps in records of Odonata species found across the state of Michigan. Below, Darrin O'Brien writes about their findings and how they surpassed 40,000 data records with the samples from our collection.

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2023 stream sampling event along the Cedar River

​Little Forks Conservancy (LFC) has been performing stream monitoring of invertebrates for multiple years as an extension of the MICorps program. Macro-invertebrates are collected in spring and fall at designated survey sites along the Cedar River each year, and specimens are identified to taxonomic family level. Since different families of aquatic invertebrates have various water quality requirements and sensitivities, this monitoring provides insights into river system health and changes.
 
Fortunately, the specimens are preserved in alcohol for potential future review. This is where we, as managers of the Michigan Odonata Survey (MOS), come in. The goal of the MOS project is to document all the species of Odonata (dragonflies and damselflies) in Michigan by county, based on voucher specimens; the current Michigan list stands at 170 species. The project began in 1996 with a compilation of vouchers from major university collections. We have been involved with MOS for over 20 years, took over the project in 2018, and have recently been working on locating and collecting data on nymphs and exuviae (the shed exoskeletons of odonates left behind as they transition from aquatic nymph to flying adults). While adult odonates may range far from water, nymphs and exuviae are found where they breed, important for determining habitat requirements.
 
Given the number of samples collected in the Cedar River by the LFC surveys, we suspected it was possible to find some significant records. We examined 66 vials from six survey sites in Gladwin and Clare Counties. The oldest samples were from 2015 and the most recent were from fall 2023.

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Rusty Snaketail nymph. Photo by Darrin O'Brien

​We looked at 272 nymphs, generating 138 records. Each record represents a unique taxa (but possibly multiple individuals) at a particular location. Of those 138 records, 137 were identified to species, and one just to genus. Of the species identified, there were two 1st county records, four 2nd county records, and four 3rd county records.  The first county records brought the total number of Odonata species vouchered in Gladwin county to 64 and Clare county to 48.
 
Significant records included:
- Zebra Clubtail (Stylurus scudderi): 1st county record for Gladwin county.  This is southernmost voucher of this species in Michigan.
- Twin-spotted Spiketail (Cordulegaster maculata): 1st, 2nd, and 3rd county records in Clare county.
- Rusty Snaketail (Ophiogomphus rupinsulensis): 2nd and 3rd county records in Clare county.
- Dragonhunter (Hagenius brevistylus): 2nd and 3rd county records in Gladwin county.
- Fawn Darner (Boyeria vinosa): 2nd and 3rd county records in Clare county.  With the addition of the LFC data, MOS surpassed the 40,000 record mark and it was likely one of the Boyeria vinosa specimens.
 
The Odonata identification exercise was a success given the number of significant finds in the LFC collection.  We hope to continue collaboration with LFC by reviewing future samples.  No doubt there are more discoveries to be made.
 
You can learn more about the Michigan Odonata Survey at our website michodonata.org, and our broader work with insects, particularly dragonflies and damselflies, at our blog Urban Dragon Hunters (urbanodes.blogspot.com).

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Article by: Darrin O'Brien, Adjunct Curator at the Albert J. Cook Arthropod Research Collection at Michigan State University