bees – Maryland Grows

Buzzing with Life: Microbes Inside a Bee’s Gut

July 25, 2025Maryland GrowsLeave a comment

Bees aren’t the only pollinators, but 87% of flowering plants rely on animals for pollination—with bees doing a large share. Their role in global crop production, worth $200 billion annually, makes them a major research focus. In recent years, scientists have turned their attention to bee microbiomes—communities of microbes living in and on bees, including bacteria, fungi, viruses, and archaea—to understand how they support pollination and health in a changing climate.

There are over 20,000 bee species, with 77.4% being solitary, such as mason or mining bees. However, honey and bumble bees, which are social, dominate research—54% of it—even though honey bees aren’t native to the U.S. Despite this, they’re essential to modern agriculture and are more abundant than ever. While native bees were often overlooked due to their lesser economic value, research on these species is growing.

Like humans, bees rely on gut microbiomes for health. A microbiome is a community of microorganisms that live on and inside a larger organism. These microorganisms, or microbes– bacteria, fungi, viruses, etc.– acquired mainly through flowers, aid in digesting tough pollen grains and help bees build fat reserves. Healthy microbiomes also offer protection against pathogens, with bacteria like Lactobacillus acidifying the gut to ward off parasites.

A graphic showing the relative populations of 14 fungal genera on flowers and bee provisions like pollen and honey, and inside bees.

Flowers serve as transmission hubs for both helpful and harmful microbes. For bumble bees, some flower-produced yeasts increase visitation, though possibly at a cost to seed production. Plant pathogens may exploit bees by overwintering in their nests, demonstrating that even mutualisms can have downsides.

Microbiomes vary by geography, bee species, life stage, and social role. For example, queen bees—fed royal jelly—host different microbes like Bombella apis, which survives in that unique diet. During metamorphosis, bees reset their microbiomes and rebuild them through interaction with the colony and environment.

Two graphics showing that bee gut biomes are less diverse when hives are treated with antibiotics and pesticides.

Human activity significantly affects bee health. In apple orchards, fungicides—though deemed safe for adult bees—disrupt brood cell microbiomes. Glyphosate, a widely used herbicide, alters bacterial diversity and reduces bees’ immunity. Contaminants from wastewater, like heavy metals and antibiotics, further disrupt microbial balance. American bees, often treated preventively with antibiotics, show more antibiotic resistance than their European counterparts, raising concerns for long-term health.

Not all findings are bleak. Probiotic and prebiotic supplements—like acacia gum—show promise in strengthening bee immunity and digestion. Probiotics are microorganisms that benefit their host, in this instance, bees, while prebiotics are food for the microorganisms. These additions enhance foraging, pathogen resistance, and overall colony resilience by supporting beneficial gut microbes.

Studying bee microbiomes helps us better protect pollinators. It also reminds us to reduce pesticide use and care for even the smallest organisms. Healthy microbes are crucial—not just for bees, but for entire ecosystems, including our own.

Resources

Bees just wanna have fungi: a review of bee associations with nonpathogenic fungi by Danielle Rutkowski, Makena Wetson and Rachel L. Vannete

Want to Save the Bees? Focus on Habitat, Not Honey Bees by Rich Hatfield and Matthew Sheperd

Microbiome by Julie Segre

Honey Bee Nutrition by Zachary Huang

In Defense of Plants: Plants, Bees and the Microbes They Share with Quinn McFrederick

Matters Microbial #6: What’s the buzz on honey bee microbes? with Irene Newton

Glyphosate and a glyphosate-based herbicide affect on bumblebee gut microbiota by Marjo Helander et. al

Glyphosate induces immune dysregulation in honey bees by Erick VS Motta, J Elijah Powell and Nancy A Moran

Uptake of the Plant Agriculture-Used Antibiotics Oxytetracycline and Streptomycin by Cherry Radish-Effect on Plant Microbiome and the Potential Health Risk by Lichun Yin et. al

Probiotics positively influence honeybee health, Western research finds by Western University

Effects of Prebiotics and Probiotics on Honey Bees (Apis mellifera) Infected with the Microsporidian Parasite Nosema ceranae by Daniel Borges, Ernesto Guzman-Novoa and Paul H Goodwin

By Lexie Leeser, Agent Associate and Master Gardener Coordinator, Baltimore County, University of Maryland Extension.

What’s the Buzz Going On in My Front Yard?

June 13, 2025Maryland Grows2 Comments

Early spring, you might notice curious little mounds of finely textured soil dotting your lawn or garden beds. If you look closer, you may even catch a tiny bee poking its head out of a hole like a groundhog (although one that doesn’t eat your plants) on the first day of spring. Don’t be alarmed and don’t stomp them out. They’re native ground-nesting bees, and if you’re lucky, they might be the charming, adorable, and important cellophane bees.

A cellophane bee looking at the camera at the opening of her nest in bare soil. — Cellophane bee emerging from nest

Meet the cellophane bee

Cellophane bees (Colletes sp.) are solitary, ground-nesting native bees that emerge in early spring. They are generalist pollinators, visiting a wide variety of plants, including early blooming trees, native wildflowers, and even some fruits and vegetables.. They’re medium-sized bees with a somewhat fuzzy appearance and are often mistaken for honey bees, though they lack the social structure and communal hive of honey bees.

Top view of a female cellophane bee creating a tunnel in bare soil to build a nest for her brood. — Cellophane bee digging tunnel

What makes cellophane bees stand out among other bees is their unique nesting behavior. Female cellophane bees dig slender vertical tunnels into well-drained or sandy soil, creating brood cells lined with a natural waterproof secretion. This lining hardens into a thin, clear layer that looks and functions like cellophane, hence its name. It helps protect developing larvae from moisture and microbial threats.

A small hole in bare soil with a low mound of soil piled up around the hole. The hole was made by a cellophane bee. — Cellophane bee hole

Now, why all the buzzing around?

Cellophane bees are solitary, meaning each female builds and provisions her own nest. However, individuals may choose the same area, leading to what looks like a large colony. This clustering behavior can surprise homeowners who suddenly see dozens of small holes in one relatively small patch of soil. While it may seem like they are swarming, these bees are not defending a hive, so they have no reason to sting unless directly handled or severely threatened, and even then, only the females can sting, and they are typically extremely docile. Because they tend to stay close to their nesting sites, they can be incredibly effective at pollinating your immediate landscape. These bees are also a reminder that supporting pollinators isn’t just about planting flowers. It’s also about providing habitat for them, and in this case, a patch of sandy soil.

Most activity happens over a brief few weeks in the spring. Once the females have mated, dug their tunnels, and stocked the brood cells with pollen and nectar, they seal them up and die off, leaving the next generation to develop underground until the following year. By early summer, all visible signs of their presence have vanished and moved underground where the larvae develop, until next spring’s return.

Live and let buzz

Let the bees live, but also support their habitat:

Leave some bare or lightly vegetated ground in sunny, undisturbed areas, grassy yards, or pathways. Over-mulching or frequent tilling can destroy nesting sites.
Avoid using broad-spectrum insecticides when pollinators are active.
Plant native early bloomers to provide nectar and pollen when cellophane bees emerge.
Resist the urge to mow or disturb nesting areas for a few weeks during peak activity (typically March through May). Mowing can destroy nesting sites and cause tunnels to collapse.
Educate neighbors and fellow gardeners about these beneficial bees, so they are not confused with infestations and treated as such.

So, if you catch sight of a tiny bee carefully peaking its head out of a little dirt tunnel in your yard this season, take a moment to appreciate it. That bee is one of Maryland’s native pollinators, doing its part to keep your garden and the larger ecosystem buzzing with life.

Written by: Hayden Schug, AgFS Educator and Julia Rycyna, Home Horticulture Educator, both with UME, Charles County. Photo credits: Hayden Schug. Article previously published in the University of Maryland Extension Charles County Connection newsletter.

Community Partnerships for Pollinators

September 9, 2024September 9, 2024Maryland GrowsLeave a comment

When we talk about pollinators and how to help them, we have often focused on what plants can support them, who the pollinators are and some traits of their natural histories, or how to create habitat for them. However, besides individual actions that people can take to help them, other options that are very impactful also exist. In today’s post, I want to present one that involves a combination of community and institutional collaboration: the Bee City and Bee Campus USA certification.

What are Bee City and Bee Campus USA?

The certifications called Bee City and Bee Campus USA are labels that cities and campuses, respectively, can receive from the Xerces Society if they commit and act to protect pollinators and their habitats.

For those who have never heard of it, the Xerces Society is an organization interested in the conservation of invertebrates and their habitats. Over the years, it has not only become recognized as an important conservation organization but also has developed impactful and meaningful ways to support research on the topic and engage the population and institutions (and many other stakeholders!) in conservation actions that are within their reach. The Bee City and Bee Campus certification is one of those initiatives.

How does it work?

Once cities and campuses decide to receive the certification, they need to submit an application and pay an annual fee. By doing this, they commit to taking specific actions that will lead to the conservation of the thousands of species of bees and other pollinators that exist in the USA, as well as their habitats. The certification is revised every year, and if the institution or city is not performing following the set standards, the certification is not renewed. Today, many institutions and cities across the USA have joined the initiative and are actively following their commitments. If you are interested in knowing if your community is a part of the initiative, an online database exists where it is very easy to search for participating members using addresses or names.

*The Bee City and Bee Campus USA website has a neat tool to search for current members across the USA.*

The commitments that institutions and cities make when they join the initiative involve the establishment and promotion of specific actions. These actions combine institutional and community involvement, which requires the creation of an active committee that will be responsible for running programs that will help the institution reach its goals. Once this committee is created, the group is responsible for proposing and running actions within the reach of the institution. The actions need to be oriented towards promoting the protection of pollinators and their habitats through what can be generally categorized under education, direct action, community involvement, and potential revision of standard operating procedures or policies.

The Xerces Society doesn’t just provide a certification. In fact, it has over the years produced a massive number of tools that help cities or institutions understand how to run the programs. Regular webinars are organized, fact sheets distributed, general manuals and other documentation shared, and a network of participating cities established, allowing for a “hive mind” to develop.

What can some of these actions be?

Education programs involve the distribution of information among the population (for cities) or members of the campus (for campuses). This information can take many different forms but generally educates about the diversity of pollinators, the importance of promoting habitat, the key contributions of pollinators to the well-being of the community and the environment, ways to protect them through individual or joint actions, creating information guides and fact sheets, and more.

Direct actions often require involvement of the institution in establishing habitat for pollinators, distributing resources that will allow the community to protect pollinators (e.g., distributing plants, seeds, other habitat resources), actively reducing the use of pesticides, etc.

Community involvement is promoted by any program that the institution could build to allow its members to come together and engage in projects larger than any individual would be able to take on by themselves. There are many ways this can be done, but some examples are the creation of student-faculty groups that could run research projects that can then be used to inform policies and conservation actions. Others could be the establishment and promotion of institution-wide actions, such as the promotion of months with no or reduced mowing (e.g., “No-Mow Month” initiatives), the running of citizen science projects (e.g., through iNaturalist), establishing days centered around the celebration and recognition of pollinators and their services to humans and the environment (e.g., coordinating Pollinator Week activities), and others.

Finally, one of the unique reaches of this initiative is its ability to promote changes of policies and procedures regularly used by the institution/city. Under this program, the committee should propose and the city or campus implement at least some adjustments in the way the institution in question is run. For example, Integrated Pest Management (IPM) plans should be created and used if they are not already in practice, Code can be adjusted to facilitate the planting of native plants, monetary or other incentives can be offered for the creation of pollinator habitat, and more.

I would like to have my city/campus join; what do I do?

If you’re interested in having your campus or city join the initiative, first go to the Bee City/Campus website and check out the requirements and some of the how-to webinars. Along with this, for cities, you may want to get in touch with representatives and present this as a request. If you’re on a campus, get a diverse group of members together and propose this to leadership. If you still feel overwhelmed by this and feel you still have a lot of questions, reach out to Bee Cities or Bee Campuses in your area and ask them for help! They will be more than happy to explain what their path was and how they came to be, so you can also become part of the national initiative.

By Anahí Espíndola, Associate Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

The Shared History of Wasps and Bees, And How Bees May Have Become Vegetarian

May 13, 2024May 10, 2024Maryland Grows2 Comments

We may have all found ourselves in that situation in which we see an insect on a flower and we wonder whether it is a wasp or a bee, and we may have also seen people panic when they encounter a bee, thinking that it is indeed a wasp. Although the two groups are very distinct and there are several ways of telling them apart (check out this previous post to see how to do it), this difficulty is in part a signature of the shared evolutionary history that the two groups have. In today’s post, I want to tell you about the evolutionary origin of bees, how it is interwoven with that of wasps, and how evolutionary studies can help us understand and explain the diversity of our charismatic bees.

Evolutionary histories and the big family we are all part of

Before jumping into the main topic of this blog, please bear with me so I can give you a bit of context for what I’ll tell you, and so you can fully appreciate the power of the discoveries I will tell you about in just a second. One of the foundations of today’s biology and the way we understand life is that living organisms share a common ancestry and that evolutionary processes such as natural selection, mutations, dispersal, and random processes have led to the establishment of new lineages that can evolve into new species and new groups of organisms. What this means is that all the living organisms we know can be placed in a sort of genealogical tree, where more closely related species and groups appear placed on branches of the trees that are also closer to each other (we call these trees “phylogenies” or “phylogenetic trees”). Also, this means that if we were to take these trees, and we were to follow the evolutionary process “backward” (from the tips to the internal branches; that is, from the present into the past), we would be able to identify branching points, which represent the now extinct ancestors of species we know today.

a diagram of a family tree — A phylogeny can be compared to a genealogical tree we may want to build for our family. In this tree, the most closely related members of our family share recent ancestors (marked with diamonds), but are still connected with more distantly related members of the family with longer branches and other more ancient shared ancestors. In the same way, a phylogeny represents the relationships between species or groups of species, with branches connected by their shared ancestors. Image: University of Iowa

Although this may sound like a biological nerd moment of mine, I hope that you will appreciate the enormity of this principle. This simple concept indicates that each of us and all species that exist on the planet have shared ancestors at some point in our history. We are all related to each other, like a huge family… and as for all families, the study of our history can teach us fun and interesting things about who we are, helping us understand and explain things we observe today. Let me tell you what the study of these phylogenies has taught us about wasps and bees (and their shared history) and why this excuses us in part from not always being able to tell them apart 😉.

Bees and wasps, and the vegetarian wasp

As you may know, bees and wasps are both insects that belong to the order Hymenoptera. Despite the fact that people knew they were related but distinct from each other, it was not until relatively recently that people understood what that relationship was. In fact, because they share a lot of common traits, scientists were for a long time confused about what the most closely related group of Hymenoptera was for bees, wasps, and ants. Some years ago, with the development of new methods that allow for more detailed studies of phylogenies, researchers found strong evidence that ants are a group of organisms that is related but distinct from another group formed by bees and by a particular group of solitary and usually ground-nesting wasps called crabronids. Besides the taxonomic and purely conceptual importance of this discovery, what this meant biologically was on the one hand, that bees are evolutionarily extremely closely related to wasps, to the point that we could consider them “non-carnivorous wasps”. On the other hand, this discovery showed that all bees we know today would have evolved from a wasp-like ancestor that was solitary and ground-nesting, like the crabronids we know today.

a family tree of bees and wasps - showing evolutionary relationships — In 2017, Branstetter and collaborators used phylogenies to demonstrate that all bees and a group of wasps (crabronids) shared a common ancestry, indicating that bees can be considered a type of “vegetarian” wasp. In the figure, the position of the common ancestors is shown with arrows and stars. The main groups are labeled on the left. Image: modified from Branstetter et al., 2017

If you’re like me and find this fun, keep reading because it gets even more fun! 😊 So, after this discovery, the people who work on these topics wanted to know more. For example, can phylogenies tell us more about how the transition from a meat-based diet (wasps are carnivores) to a pollen-based one (bees feed mostly on pollen and nectar) could have happened? To investigate this, researchers ran a similar analysis, but this time considering a lot more species of both bees and crabronids. Constructing phylogenies using genetic information, they figured that when the evolutionary relationships of these groups were studied, it appeared that bees were the most closely related to a particular group of crabronids that is known to predate on thrips (a family called Ammoplanidae).

a closeup of a small black bee — Bees have been shown to be very closely related to a group of tiny wasps in the family Ammoplanidae which are known to hunt on thrips. Photo: CBG Photography Group (CC).

Besides confirming the discoveries of the previous study, this one provided a logical and interesting biological and ecological context for the transition from carnivory to pollinivory in bees. Thrips are a group of insects known to feed on plant materials, often found on flowers, where they feed on pollen. This new study proposed that a possible evolutionary opportunity may have appeared when a lineage of thrip-predating wasps evolved the ability to not only digest thrips meat but also the pollen they contained in their guts (!!). This transition could have set the evolutionary foundations to eventually transition to a diet fully based on pollen, which opened opportunities to the newly emerging lineage to feed on a new dietary resource not already in use by other wasps. If this is true, this transition would have provided an important evolutionary advantage (e.g., reduced competition for food), which would have led to the huge diversification of bees, leading to the extreme diversity we see today.

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Waiting on Spring Garden Cleanup to Support Beneficial Insects

April 15, 2024April 15, 2024Maryland Grows1 Comment

With warmer temperatures and spring blossoms we are likely ready to get back into our gardens. Before we get our hands dirty, let’s learn how to support the beneficial insects in our landscapes that are and will be emerging from their overwintering sites. In today’s post we will review some information and tips on how we can support, and not disrupt, the life cycles of beneficial insects like our native bees, when we do any spring garden cleanup or prep.

Plant stems, leaves, and other debris can be home to many beneficial insects during the winter months that are waiting on warmer days before they emerge this spring. Wait as long as you can before removing any plant materials. Photo: M.E. Potter, University of Maryland Extension

Overwintering beneficial insects

Some insects migrate (e.g. Monarch butterfly) to avoid the cold temperatures, but there are many insect species that overwinter (spend the winter months in one of their life stages- egg, larva, nymph, pupae, or adult) in Maryland. Insects like luna moths (Actias luna) who overwinter in the pupal stage in cocoons within leaf litter (see photo below), the great spangled fritillary (Speyeria cybele) who overwinters as caterpillar larvae in leaf litter, bumble bee (Bombus spp.) queens who can overwinter as adults underground, small carpenters bees like Ceratina strenua who overwinter as adults in plant stems, and praying mantids like the Carolina mantis (Stagmomantis carolina) who overwinter in the egg stage as ootheca (an egg case) laid on woody plant stems and other structures. All these examples are of beneficial insects, who provide services like pollination and pest control during their active life stages. This goes to show, even in the cold and quiet winter months, your garden can be full of life!

a luna moth cocoon found in fallen leaves — *Luna moths overwinter as pupae in cocoons made of fallen leaves and silk. In late spring the insect will emerge as an adult moth. Photo: M.J. Raupp, UMD*

When is too early for spring cleaning?

Generally, the longer you can wait the better! Insects do not all emerge at the same time. There are some native bee species that emerge from their overwintering sites as early as March (e.g. some Colletes spp.) and some that typically do not emerge until late May (e.g. Blue-green sweat bees). Due to the changing climate and the diversity of insect life cycles, we unfortunately cannot point to a specific date on the calendar to know all the overwintering insects have emerged from our green spaces. We can look for different cues in our environment to hint at insect emergence.

Before last frost and consecutive warm days

Once we are out of risk of evening frosts and daytime temperatures are consistently above 50°F for several days in a row, many insects will begin to emerge. Otherwise leaf litter and other plant debris are vital for overwintering insects to survive the cooler temperatures. With climate change, and the chances for more drastic temperature changes, fallen plant material becomes even more important for protecting overwintering insect populations. Think of a fallen leaf as a blanket for our beneficial insects!

Looking for spring blooming trees like cherry, peach, or eastern redbuds can clue us in on this year’s seasonal changes and timing when it comes to insect emergence. Once fruit trees have finished blooming, many of our overwintering bees and beneficial insects have likely emerged. Photo: Nancy Lee Adamson, Wild Bee Plantings

Before fruit trees bloom

Many of our fruit trees (along with natives like Eastern redbud and red maple) bloom in early spring, providing nectar and pollen for our early riser pollinators; check out the figure below on native bee and orchard bloom phenology. If you wait for any garden cleanup until these trees have finished blooming (around mid-May), many of our insects will have likely emerged by then. Since phenology (seasonal changes in a plant’s life cycle, such as the timing of bloom) can shift with changing climate conditions, always keep an eye on the trees and blooms around you. A great excuse to get outside and get to know your local plant life.

Before consistent lawn/turf growth

Noticing consistent lawn/turf growth in your area? Cool-season grasses begin their spring growth once soil temperatures are between 50° and 65°F. A general guideline is once lawns need to be mowed it is a good sign it has been warm enough for many of our overwintering insects to emerge. If you have lots of lawn in your space, consider reducing and replacing the lawn with beneficial insect friendly native plants! If you are wondering what you could plant instead, check out Lawn Alternatives. And if you have heard of No-Mow May, check out the Pros and Cons of the No-Mow May Movement and the Controversy Surrounding No Mow May, by Dr. Gail Langellotto.

Sometimes less is more

Less garden cleanup can have a positive impact on beneficial insect populations! Rethink removing plant debris in certain areas of your landscape. Unless the plant debris comes from a diseased or pest infested plant, leaves, stems, sticks and more can be left, relocated, or reused as wildlife habitat. Your plant debris is some animal’s home! Preliminary data from a study conducted by Max Ferlauto, PhD student in the Burghardt lab, at the University of Maryland, Department of Entomology, shows the number of emerging moths and butterflies are reduced by approximately 67 percent in areas where leaves are removed. If you are removing any plant material, consider relocating the materials to an unmanaged, “habitat area”, or to a compost pile after late spring.

Help fight climate change’s impact on beneficial insects by providing shelter to help insects withstand adverse conditions. Consider leaving and/or adding one or more of the following sources of habitat in your green space this spring!

Leaves
Flower stalks/plant stems
Fallen/removed twigs
Wooden logs
Rocks/rock piles

From “messy” to sustainable

If you are worried about your space looking messy from less spring cleaning, there are ways to get creative to transform your and the public’s view of your conservation areas. An opportunity to personalize your green space with unique and practical “signs of care” (also known as “cues to care”).

Signage

A sign in your green space can not only enhance the look but also help educate others. Why are you leaving the leaves? Let others know by adding a sign about how leaves support native wildlife. Look to local artists and organizations to find a sign that works for your space and could convey a science-based message. You can earn a sign from our Bay-Wise Master Gardener program once your landscape is Bay-Wise certified. To learn more, check out our Bay-Wise program page.

Fencing or edging

Even a short fence or edging can make a space look purposeful and cared for. Edging can be made out of repurposed materials (pebbles, stones, sticks, even glass bottles) or can be purchased from most gardening centers or hardware stores. Think of it as putting a frame around the artwork and beauty that is your garden. For ideas check out, Edging Makes Landscape Beds Pretty, Easy to Keep or Landscape Edging Materials.

Tidy, accessible paths

Ensure any pathways, especially areas around public sidewalks, are clear so all can access and enjoy the space and surrounding area. Cut back overgrown plants that may be blocking or obstructing pathways. If you are working in a community garden, consider the accessibility of your landscape so we may create more inclusive green spaces for all. To learn more about accessible green spaces, check out these pages, Create an Accessible Garden for Those of all Physical Abilities and Gardens Are For Everyone: Ideas for Accessible Gardening.

Additional resources

By Madeline E. Potter, M.S.,Faculty Specialist for Entomology and Integrated Pest Management, University of Maryland Extension

Research Update from the Serpentine Grasslands: Pollinators in a Rare and Endangered Habitat

April 8, 2024April 4, 2024Maryland GrowsLeave a comment

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!

a view of the Maryland Serpentine Grasslands on a cloudy day — *A stormy summer evening at Soldiers Delight Natural Environment Area, Baltimore Co. – one of Maryland’s Serpentine preservation areas. Photo: Justin O’Neill*

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?

a purple wildflower found in the Maryland Serpenine Grasslands — Phemeranthus teretifolius, the Quill Fameflower, is one of the special plants that makes its home on the dry and rocky soils of Serpentine habitats. The flower is only open during a few short hours in the afternoon, during which it is abuzz with small solitary bees. Photo: Justin O’Neill

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.

a student researcher collecting insects at the Maryland Serpentine Grasslands — Nets at the ready! The Serpentine squad carefully captures bees and hoverflies seen visiting flowers at several study sites across three of Maryland’s Serpentine conservation areas. Photo: Justin O’Neill

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.

close-up of the face of a bee found in the Maryland Serpentine Grasslands — *A close-up shot of a fluffy male Andrena gardineri specimen. Photo: USGS Bee Monitoring Lab / Brooke Alexander.* *CC 2.0*

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!

another bee found in the Maryland Serpentine Grasslands — *The waspy-looking Nomad bee: Nomada seneciophila. Photo: Justin O’Neill*

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.

Stem-Nesting Bees in Maryland

March 11, 2024March 8, 2024Maryland Grows1 Comment

With their large diversity, bees display a huge variety of nesting preferences. Some bees that are relatively commonly encountered in our region are those that nest in stems. In today’s post, I want to tell you about who they are, their biology, and their preferences when the time comes for them to pick their nesting sites.

Who are the stem-nesting bees in our region?

When we consider bees that nest in stems, we can think about two main groups. In the first group, we have bees that actively dig into pithy stems or wood to build their galleries. In the second group, we have those that use pre-existing cavities in stems and slightly adjust them to accommodate their brood. This difference may seem trivial; at the end of the day, they will all end up in stems, right? Well, that is true to some extent; however, whether we talk about one group or the other will define what actual taxonomic group of bees we’ll be referring to, and a different set of morphological adaptations that allow them to build their nests properly.

In our region both types of bees are present and many of them are relatively common and easily observed in our green spaces.

Stem nesters that dig their nests

In addition to large carpenter bees (Xylocopa), this group includes Halictid bees such as Augochlora and the Apidae Ceratina. Because they all have to dig actively into stems to build their nests inside, all these bees are equipped with very strong mandibles, which have modifications that reinforce them, and strong muscles that allow them to increase the force they can exert on the stems.

a metallic green bee going into a stem nest cavity — Metallic bees are very common in our region. They often can be found emerging or looking for wooden resources to build their nests. Photo: K. Shultz (CC).

Depending on the species, we can find them building nests on different substrates. While Augochlora can often be found building galleries in rotten logs, Ceratina is mostly associated with stems that tend to be a bit hollower, such as those of raspberries and blackberries (you can check out this other post on how to trim those plants to protect their nests), or those of plants of the genus Verbena. In all these cases, the nests have the shape of a gallery, with small cells built consecutively. Each of these cells is carefully built, provisioned with nectar and pollen, populated with one egg, and finally sealed with sawdust or compacted pith.

Stem nesters that use stem cavities that already exist

Several families of bees belong to this group in the Mid-Atlantic. Species of the genus Hylaeus in the family Colletidae are present in our region, and readily nest in hollow stems. Another group that is very commonly seen in our region is that of leaf-cutter bees (Megachilidae). Although this group tends to be more flexible in the types of cavities they will use for building their nests, many species will readily use natural or artificial “stem-like” cavities (these bees are very common in bee hotels).

several bees nesting inside of a plant stem — A small bee commonly seen in bee hotels is that of genus *Hylaeus*, also known as the yellow-faced bees. These bees will readily use small hollow stems and cavities. Photo: R. Cruickshank (CC).

Stem-nesting bees (Hylaeus) were observed in a raspberry cane on May 10, 2023, in Montgomery County, MD. Video: Christa Carignan, University of Maryland Extension

Because these groups do not need to actively dig into wood to build their nests, their mandibles are not as developed as those of the other group of bees I presented above. A common characteristic of all these bees is that they have relatively long and slender bodies, which is believed to allow them to move with more ease in relatively small cavities. It is also for this reason that specialists think that all these species transport pollen either internally or on the lower part of their abdomens (instead of on their legs, for example); this reduces their “width” and allows them to fit into cavities that may otherwise be too narrow. Another characteristic of this group of bees is that they often line their brood cells with special materials, such as leaves, petals, resins, or mud. This means that building these nests is a lot of work!

leaf-cutter bee carrying a leaf piece to a nest — Leaf-cutter bees of genus *Megachile* are also very commonly seen in bee hotels and nesting in cavities around our homes. Here, *M. centuncularis*, brings leaf cuttings to line the nest in a cavity offered in a bee hotel. Photo: B. Plank (CC).

Although bees (and most insects) are generally negatively affected by urbanization, this group of bees appears to benefit from their interactions with humans. Unlike ground-nesting bees which are very negatively affected by land development and urbanization, it seems that stem-nesting bees can easily use many cavities created by humans, such as those appearing in buildings, walls, fences, and gardens.

Read more: This Year, Host Bees in Your Garden

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an award-winning Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

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