Did you know that before European colonization and thanks to native land management, the area that is now northern Maryland was home to thousands of acres of sprawling prairie-like grasslands? It’s a pretty cool thing to imagine, right? Instead of dense urban centers, highways, farms, and patches of forest, most of Baltimore County would’ve been a nearly treeless ocean of swaying grasses and wildflowers! Instead of cars, shopping carts, and the hustle and bustle of people, you’d see majestic herds of deer and elk, a horizon dotted with flocks of birds, and the busyness of bees and butterflies. You can read more in a previous blog post about these eastern ‘Serpentine Grasslands’. Sadly, these grasslands no longer exist in the formerly massive extent they used to occupy, but several preserved remnants still endure here in Maryland to tell the tale of their former glory!

What is the current status of the Maryland Serpentine Grasslands?

Many historic and contemporary human-driven environmental changes have caused these special ecosystems to dwindle to the point of concern; it is currently estimated that only 1.6% of their historic area in the region remains. This precipitous decline of eastern Serpentine Grasslands is concerning because they support many special plant species that are considered threatened or rare in Maryland. Luckily, several private and governmental organizations have taken to conserving and studying these ecosystems in Maryland and elsewhere (check out some of them here: Soldiers Delight and Lake Roland). Although eastern Serpentine grasslands have attracted considerable scientific research interest in terms of their rare and unique plant life, the animals that call these critically imperiled habitats home are virtually undocumented (with the exception of some rare butterflies and moths). Could there be special Serpentine associated species that we have yet to even notice?

The mission of knowing what lives there to better protect it

To address this knowledge gap, our team at the EspíndoLab, have set out to start documenting the insects present in Maryland’s Serpentine Grasslands. Our current focus is on flower-visiting insects that could act as pollinators, specifically bees and hoverflies. Given the many rare and threatened plants documented in these areas, we figured it was important to first know what insects might be helping most with Serpentine plant reproduction. 

How do we do this?

To document these flower-visiting insects, the lab crew has undertaken 5 years (2019 – 2023) of observations and insect collection in three of Maryland’s most intact Serpentine Grassland conservation areas. Because different flowers bloom during different parts of the growing season (spring to fall), we had to visit these conservation areas many times each year to observe the full range of flowering plants and their insect visitors. So, once every two to three weeks across each season, the Serpentine squad would head out to visit our many field study sites and systematically capture bees and hoverflies seen interacting with flowers. Currently, we are working on the meticulous process of examining each captured specimen with a microscope to determine its species identity using taxonomic guides.

With this information we can begin to catalog the insect species that make up Serpentine pollination communities. This allows us to explore if the communities present in the Serpentines are different from those in nearby habitats and if they possess any rare or unique species. This information will also give us insight on how the plant and pollinator communities interact with one another; informing us about key species that contribute vitally to pollinator persistence or plant reproduction. Ultimately, the knowledge we gain will provide a baseline understanding about the dynamics of pollinator diversity in the grasslands and inform the organizations that conserve and restore these ecosystems.

What are we learning?

So far, the EspíndoLab’s efforts in the grasslands have revealed quite a bit about the broad array of insects that visit these unique plant communities. Notably, among the myriad of beetles, butterflies, flies, and wasps that visit Serpentine flowers, native solitary bees and hoverflies are consistently observed to be the most abundant – and perhaps most important potential pollinators. Interestingly, social bee species, particularly honey bees, that are commonly observed in many pollination communities, were infrequently encountered in our collecting efforts until late in the season, if it all. This suggests that they may pass on the relatively sparse floral resources of the grasslands until the Fall, when dense and attractive patches of goldenrod and aster bloom – potentially providing them an important source of resources as pickings become slim late in the season.

Most excitingly, our collections have revealed 39 unique genera of bees and hoverflies in the grasslands, so far – with more likely to be found as we continue to identify the many insects from our collections. Our efforts have also found several rare bee and hoverfly species; some of which are insects that have never been observed in Baltimore County! Among these rare and interesting finds are two bees and a hoverfly that are particularly special.

The hoverfly, Trichopsomyia litoralis, is relatively new to science – having only been described in 2019. Not much is known about the ecology of this species, but its larvae are known to feed on economically important pests. Encountering this species in the Serpentine grasslands is interesting not only because it is rarely observed, but also because it is currently thought to only inhabit an eastern coastal range (likely associated with sandy sites)! This information could extend our understanding of this hoverfly’s distribution or suggest that these flies undertake long migrations during their life cycle.

On the other hand, we have found two rare bee species that are really cool: the mining bee, Andrena gardineri; and the nomad bee Nomada seneciophila. These bees are what we call specialists: they have very specific ecological requirements. For example, A. gardineri is known to preferentially forage for pollen on plants from the genus Packera (ragworts or groundsels) – it is considered a Packera specialist. Even though A. gardineri is quite rare in the region, we find it commonly during our spring grassland collections. This is because almost all the conserved grassland areas provide good conditions to host lots of Packera anonyma.

The other notable bee we observed, the nomad bee, Nomada seneciophila is a vanishingly rare cuckoo bee (see here what these bees do and why this is fascinating). These bees wander (nomadically so) around in search of other bee’s nests so they can hijack them for their own young to develop in! N. seneciophila, as it turns out, is a specialist of our specialist friend, A. gardineri. That is, this nomad bee species has a very strong preference for stealing the nests of our other rare bee, A. gardineri!

From these interesting encounters, it is becoming increasingly clear that these grasslands not only support remarkable plants; they also provide critical resources and nesting habitat for rare bee and hoverfly species. Although these once expansive ecosystems might not exist on the grand scale they once did, their remnants are unique contributors to the region’s biodiversity. Taking the time to document their floristic and faunistic wonders is important for understanding the historic role they played in shaping regional biodiversity today, and how that biodiversity may respond to the changing environments of the future!

By Justin O’Neill, Ph.D. student, and Dr. Anahí Espíndola, Assistant Professor, EspíndoLab, Department of Entomology, University of Maryland, College Park.