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Hover Flies Identified: Researchers Tackle 20,000 Syrphid Specimens in Illinois Collection

Four-part image: Top left shows a hover fly with large black eyes, a yellow fuzzy thorax, and a dark abdomen, looking very much like a bumble bee, perche on a green leaf. Top right shows a pinned hover fly specimen, with a dark body covered in fine yellow fuzz, against a gray background. Bottom left shows a hover fly that is striped yellow and black across its whole body, somewhat mimicking a yellow jacket, perched on a bunch of small yellow flowers. Bottom right shows a hover fly with large red eyes, a dark thorax, and a yellow and black striped abdomen, also perched on small yellow flowers.

A trio of entomologists at the Illinois Natural History Survey tackled a backlog of hover fly specimens dating back a century, digitized them, and combined them with online databases—leading to several new species records, changes to species ranges, and even discoveries of new areas of conservation concern for hover flies in the state. In August 2023, they reported the results of their work in the open-access Journal of Insect Science. Shown here are hover flies Mallota posticata (top left), Microdon aurulentus (top right), Spilomyia longicornis (bottom left), and Toxomerus geminatus (bottom right). (Top left photo by Lee Elliott; all other photos by C. Scott Clem, Ph.D.)

By Hannah S. Tiffin, Ph.D.

Hannah S. Tiffin, Ph.D.

Hannah S. Tiffin, Ph.D.

With 7 million specimens, the Illinois Natural History Survey Insect Collection features one of the largest and oldest collections of arthropods in North America. But what good are all of these specimens in boxes and drawers in today’s era of “big data” and artificial intelligence?

With the increasing global biodiversity crisis and news of insect and other species declines, these collections can provide a critical foundation for determining species’ historical ranges, abundance, and even changes in traits through time. Additionally, with increasingly user-friendly identification apps like iNaturalist and Seek, there has been a resurgence in public interest in environmental conservation and education, thereby fueling community-science projects utilizing these apps for on-the-ground species observations.

But who is verifying these identifications? Who is identifying and cataloguing this utopia of historical specimen collections?

This is no small feat, but it was tackled head on by a team entomologists at the Illinois Natural History Survey (INHS). Like many of us, C. Scott Clem, Ph.D., and Lily Hart were sitting behind screens during the height of the pandemic, working through the Care and Curation of Entomology Collections Course at the University of Illinois at Urbana–Champaign (UIUC), taught by Tommy McElrath, Ph.D., curator of the INHS Insect Collection. Unlike most of us though, their conversations behind the screen led to a major research endeavor—to identify and re-curate the tens of thousands of hover fly (Syrphidae) specimens housed at the INHS.

Clem, a doctoral candidate at UIUC at the time and now a postdoctoral scholar at the University of Georgia, was sifting through these specimens and quickly realized that nearly a quarter were still unidentified, and all had essentially remained untouched for nearly 40 years. With the specimen abundance and diversity housed at the INHS, Clem and Hart, an assistant at the INHS Insect Collection, joined with McElrath to take on the case of the unidentified hover flies at the museum. In August, they reported the results of their work in the open-access Journal of Insect Science.

The Flower Flies

Lily Hart

Lily Hart

C. Scott Clem, Ph.D.

C. Scott Clem, Ph.D.

Hover flies are a diverse family of flies that provide a trove of ecosystem services, particularly as pollinators, earning their alternative common name “flower flies.” While the adults frequently serve as pollinators, the larvae are often efficient nutrient cyclers or can be used in biological control. This makes hover flies invaluable, not only in natural systems but in agricultural systems as well. Yet, despite their critical roles in agriculture and the broader ecosystem, there are still many unknowns associated with this family of insects.

Like most entomology collections throughout the world, INHS houses vast numbers of unidentified specimens. A strong push for collecting in the 1960s through the 1980s, combined with decreasing funding levels for taxonomists and specimen collections since the 1990s, has contributed to this backlog of unidentified insects. This is one of the reasons Clem and Hart decided to tackle this project. By identifying, cataloguing, and digitizing these previously unidentified hover flies, Hart says that this research “goes to show what a treasure trove insect, and specimen collections overall, really are,” both to scientists and to the public.

Clem also notes the sense of pride that comes with identification. “It was super satisfying to realize we reduced the unidentified specimens by half,” he says. “By more than half!” This not only reduced the unidentified specimens within the INHS collection but also led to new species records, changes to species ranges, and even discoveries of new areas of conservation concern.

The authors were able to supplement the INHS data with data obtained from iNaturalist, the Global Biodiversity Information Facility (GBIF), and other datasets to make inferences about potentially declining species and species of conservation concern in Illinois and the surrounding region. Additionally, by digitizing the INHS specimens, the researchers made the collection more accessible to scientists not based at INHS to continue to build on this research and gain a better understanding of biodiversity, natural history, and conservation needs for the future.

Specimen Collections: More Than the Sum of Their Parts

The team’s research also highlighted another important utility for specimen collections: training the next generation of taxonomists. Clem says that these types of studies make for excellent course and learning material for budding entomologists, mammologists, herpetologists, and the list goes on! By incorporating specimen collections into educational lesson plans, students can learn about local species while contributing to species identification, potentially discovering a new interest along the way. These collections really are “treasure troves” as Hart says, not just due to their immense specimen material but for the potential they provide to improve our understanding of species’ natural histories, their changes through time and place, and the abundant educational and research opportunities they provide for new and seasoned scientists alike.

Hannah S. Tiffin, Ph.D., is a postdoctoral scholar in the Veterinary Entomology Laboratory at Penn State University and a communications editor for the Journal of Insect Science. Email:

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