Author:Anahi – Page 2 – Maryland Grows

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!

Heat Waves Affect Pollination Too

August 5, 2024March 7, 2025Maryland Grows2 Comments

Having grown up in the plains of Argentina, surrounded by large rivers, swamps, hot summers and humidity, I can attest that I am pretty “heat tolerant.” While others complain of the heat, I just enjoy the “embrace” that a hot day gives me. The heat in the last few weeks, however, was even too hot for me! And while I was trying to cool down, I was also worrying about what I was seeing outside: the plants, the insects, the soil… all suffering like me. And because I happen to work on some of these topics, I also knew that it wasn’t just that some plants were drying out; this heat wave (and drought) is also affecting the whole network of interactions that happen around us. So, today let me tell you a bit about how these extreme heat waves affect one of those interactions – pollination – and how what we do in our green spaces can help reduce some of those effects to the benefit of all.

Pollination is affected by heat in more ways than we usually think

Extreme heat waves and droughts such as those we have been experiencing recently affect not only us but also the ecosystems that are exposed to the heat. One of the most evident effects we may see is how much plants suffer. Just look outside and you will see hanging leaves, tiny flowers (if any), and a lot of dry material. As with all organisms, plants also have optimal temperatures at which they can survive; if the temperatures and water availability change, important body functions will not be able to be performed, and even some central parts of their bodies will fail.

In plants, one of those functions is photosynthesis, the process by which plants can make sugar using the energy of the sun, carbon dioxide (CO₂), and water. This process is the way the vast majority of plants make their food. If the process is disturbed, the plant will have less energy available to survive, grow, and reproduce. It turns out that extreme heat and water needs affect the ability of plants to photosynthesize. The consequence of this is that, suddenly, the plant has less energy available, needing to enter a sort of “survival mode.” Along with this, the heat affects several protection systems that the plant has, especially those that protect the DNA (the genetic material), as well as the functioning of the machinery that literally “builds” the different parts of the plant. This inefficient protection leads to the DNA being damaged and the plant being poorly “built”, making that part or the whole plant start malforming.

plants with browing stems due to drought — *During the heat waves, these beebalm plants had a rough time, with almost no flowers produced and a lot of the plant material simply drying out. Photo: A. Espíndola*

In relation to pollination, we know that these changes explain why, under heat and water stress, plants become smaller in size, have tiny or no flowers, lose a lot of leaves and biomass in general, and have parts that start to look “funky.” The changes in the energy availability make the composition of some secretions change as well, such as with nectar, which tends to be less rich in sugars and less abundant (especially when drought is experienced).

a plant with smaller than usual yellow flowers — *These black-eyed Susans were able to make flowers this year, but they are significantly smaller than usual! Photo: A. Espíndola*

As said before, flowers tend to be small or absent, but even when they are present, the petals and reproductive organs are often misshapen, with the plant becoming unable to produce seeds and fruits. Finally, and super importantly for pollination, a major effect of this is that heat affects pollen quality, reducing the amount that is produced and often making the pollen inviable… meaning that even if the pollen was to land on a stigma, it would likely not germinate, and fertilization would not take place. This latter point is worrisome because it means that even plants that are not animal-pollinated (e.g., plants pollinated by wind or water) will be unable to produce seeds and fruits.

Pollinators suffer the heat, and that affects their survival and pollination

Pollinating insects are also affected by the heat, and some of these effects are related to the same facts we mentioned for plants. On the one hand, like plants, pollinators also have their own DNA and “body-building” machinery that is disturbed by heat. Some of the major consequences of this are that their development can be either interrupted (the larvae or pupae die off) or interfered with. If the development is interfered with, we see malformations in different organs, such as the wings, legs and mouth parts, and particularly in males, of reproductive organs and sperm. Further, extreme heat appears to affect bee neurological abilities, with their behaviors and memory affected, as well as changes in the way they visit and manipulate flowers, which in turn makes pollination more difficult.

Along with these issues, because of the changes in nectar quality and quantity associated with plant heat stress that we mentioned earlier, the pollinators’ nutrition is also negatively impacted, which further amplifies the developmental, behavioral, and neurological problems mentioned above. Although all insects experience these types of effects when they are exposed to excessive heat, some of them are a bit better at protecting themselves from it. For example, it seems that social bees suffer less from excessive heat than solitary bees, while bees that nest in the ground or in stems tolerate it better than those that nest in cavities.

Here’s what you can do to help mitigate the effects of heat and drought

Although we can’t instantaneously reduce the heat, we can assist plants and insects to better tolerate these conditions. A very effective strategy is diversifying our green spaces, which can lead to local reductions of heat, either through the shade created by the plants and/or the reduction of the excessive presence of bare soil. In particular, this same plant diversification can also increase the amount and quality of foods available to pollinators during these heat events: more diverse plants mean more different types of possible nectar sources available to pollinators, which in turn would increase their chances of survival and boost their health.

If possible, one can also water plants in our green spaces. By doing this, the water stress will be reduced and at least part of the symptoms displayed by plants will also be mitigated. If one were to do this, it is important to water with a slow flow and for a longer period of time, so the water can properly enter the soil. Along with this, using mulch or letting the fallen leaves cover the ground will also help retain some of the soil humidity, all while also providing shelter to insects.

And besides diversifying and supporting our green spaces, it is thoroughly accepted that the current extreme heat and drought events we are seeing are a consequence of climate change. Starting to reduce our and our communities’ emissions is another way to help plants and pollinators, pollination, and at the end of the day, the production of many of the foods we depend on. You can check out this awesome website by Dr. Sara Via and learn about what we can all do, and even sign up for super informative seminars that help you become familiar with and start acting on some of these topics.

Support Our Insects at Night

June 12, 2024June 11, 2024Maryland GrowsLeave a comment

We tend to think about protecting our insects when and where we see them. This is perhaps why we may have a higher propensity to think about protecting pollinators we can see flying around rather than organisms that live in the darkness of the soil or hidden in the leaf litter. In today’s post, I would like to bring some attention to other groups of insects we may tend to forget about but which we can also help protect: insects that are active at night.

Don’t insects sleep at night?

Although many insects are generally less active at night due to the lower temperatures and their inability to move when the temperatures drop below a certain threshold, many insects are adapted to being active at night. For example, if they are pollinators of nocturnal or dusk-flowering plants such as several moth species are, they will be active when darkness falls. Other insects are active at night as predators, or at certain times of the season looking for mates and egg-laying sites. For all these insects, the absence or reduced presence of light is important for allowing them to take on what they need to do to survive and/or reproduce. For this reason, the presence of artificial night lighting in our outdoor spaces, especially in the warmer periods of the season, can interfere with these insects, leading to potentially very negative effects.

How can outdoor night lighting affect nocturnal insects?

Insects can be perturbed in different ways through outdoor night lighting. One of them is its potential interference with their temporal rhythms. In fact, like most animals, insects use light-darkness and the presence of certain night sky cues (e.g., full moon) to regulate their developmental cycles and perceive the progression of the season. The presence of supplementary lights during the night hours can lead to altered developmental cycles, making them longer or mismatching those of organisms belonging to the same species. This can lead to the insects missing their optimal mating times, losing their ability to forage on specific plants, or properly preparing for the arrival of colder nights as the season progresses.

a string of lights is hanging over a a garden firepit area at night — The use of often non-essential lighting, such as light strings and other nocturnal accent lights in our spaces, can negatively affect the development, survival, and reproduction of many nocturnal insects. Photo: P. Danilyuk (CC)

Another issue that artificial nocturnal light can produce relates to the spatial disorientation of nocturnal insects. This can occur when insects are attracted to nocturnal light sources instead of moving towards their optimal habitat. This can lead to increased predation in those areas (the insects become more exposed to being seen), as well as their spending valuable energy by spending time in an inhospitable region. Further, disorientation can happen in a more indirect way by the light’s interference with the patterns present in the canopy. In fact, many insects have been shown to use the contrast pattern of the canopy and the sky to navigate and identify optimal habitats. The presence of nocturnal artificial lights can lead to the disappearance or a stark modification of that contrasting pattern, interfering with their ability to find their way in the ecosystem and decreasing their ability to find a proper habitat for their survival.

two fireflies light up at night — Some insects like fireflies use bioluminescence for inter-species recognition and mating. Photo: T. Ota (CC)

In some cases, the presence of nocturnal artificial light can interfere with mating and intraspecific recognition behaviors. Many groups of insects, such as fireflies and glow worms, use light cues to attract and recognize each other. In regions such as ours, where fireflies represent such an important part of our ecosystem, the use of outdoor nocturnal artificial lighting can interfere with the finding of mates and can potentially lead to much reduced abilities to reproduce and sustain populations.

What can we do to reduce this type of nocturnal pollution?

The obvious answer to this question is that if we want to reduce this type of pollution, our best bet is to turn off non-essential outdoor night lights, in particular during times of the year when insects are active. Doing this may actually save us some money, but also will allow us to support a higher diversity in our area, all while potentially letting us appreciate even more the nocturnal activity that may be present in our region. For example, doing this may make it easier to support fireflies and participate in their conservation, but can also support the reproduction of plant species that depend on nocturnal pollinators.

If leaving lights on is unavoidable, one should consider the intensity that is being used. Can the light be dimmed to a lower intensity? Could it be filtered to display a color that is less disruptive to insects? The Xerces Society has put together a really neat guide on this (Firefly-Friendly Lighting Practices – PDF), and I strongly encourage you to consult it if interested.

Finally, another way we can contribute to reducing unnecessary night lighting is by engaging in our communities. Initiatives such as DarkSky can help with this, both promoting best practices at the community level and engaging in conservation through community certification programs that are conservation-effective. You can learn more about these nocturnal conservation programs here.

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

May 13, 2024May 10, 2024Maryland Grows3 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!

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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A Little-Known Group of Pollinators: Beetles!

February 12, 2024February 12, 2024Maryland GrowsLeave a comment

As we mentioned in previous posts, when we think about pollinators, we tend to think of butterflies and bees, but rarely about the super important hoverflies or other groups of organisms. In today’s post, I want to tell you about another of those little-known pollinator groups; let’s talk about beetles that act as pollinators!

Beetles: “hard-shelled” pollinators

From a taxonomic perspective, beetles are a group of insects that belong to the Order Coleoptera. Among other important characteristics, they are recognized by their extremely well-protected body, in particular by structures called “elytra”, which provide a very hard cover to their wings (the wings are placed under the elytra). Generally, beetles have mouth parts that are adapted to chewing, which means that they have large mandibles that allow them to break their food. You may be wondering why I am talking about these structures in a pollination post… well, as for all pollinators, the shape and function of a pollinator define what they do (and don’t do). Let’s see how this affects our pollinating beetles.

a black and yellow beetle on a purple flower — Beetles are common flower visitors, with some of them being very effective pollinators. Because of their very well-protected bodies (see elytra covering the “back” of this beetle), they often spend a lot of time on flowers, where they feed on pollen, nectar, and floral parts. In this picture, we can see a cetoin scarab beetle with prominent elytra and a very hairy body that helps them transport pollen grains between flowers. Photo: C. J. Sharp (CC).

In the case of beetles, the fact that they are well protected by those elytra makes them more “confident.” That “hard shell” provides a great deal of protection against predation by other arthropods, which in turn makes them generally more “chill” in their visits to flowers. Unlike butterflies, bees, or hoverflies, beetles tend to move little within and between flowers, taking all their time to get the resources they need from them. For this reason, they are often considered as more generalist and inconsistent pollinators than their less-protected counterparts.

The shape of their mouths and their feeding habits also affect their efficiency as pollinators. In fact, beetle visits to flowers tend to be relatively destructive because they are attracted to them by their floral tissues, including in some cases pollen and the ovaries! In this respect, beetles tend to visit flowers to feed on them, which in some cases can lead to floral destruction. So, given this, are beetles good pollinators or just flower herbivores?

Beetles as pollinators

Among all the many different groups of beetles, some of them are considered to be particularly good pollinators. Specifically, these belong to the beetle families known as soldier (family Cantharidae) and longhorn (family Cerambycidae) beetles, families that depend on floral resources for their survival at least at one stage of their development. Other families such as scarabs can also be strongly associated with flowers for their survival. In all these groups, the beetles in question have clear adaptations that make them good agents of pollen transfer. For example, we observe different parts of their bodies covered with abundant hairs. This improves pollen transport and thus increases their ability to effectively cross-pollinate the flowers they visit.

a beetle with pollen grains on its head — Beetles that are good at transporting pollen have hairier bodies that can carry pollen grains, like this cantharid beetle that got its face covered in pollen while visiting these flowers. Note the yellow “powder” – pollen – that covers part of the beetle body and take a look at the large mandibles the beetle uses to feed on floral parts. Photo: J. Tann (CC).

Further, although these beetles tend to still feed on floral parts, they are usually much less destructive than their more generalist cousins. They often feed on specific flower parts (instead of on all the floral sections), leaving the central reproductive structures (e.g., the ovaries) intact, and thus allowing plant reproduction. These beetles are also often more specialized in their floral choices, preferring a small range of plant groups (usually one or a few species within the same plant genus), and moving more readily between flowers. Combined, all of this means these beetles can not only carry a lot of pollen (they are hairy) but also move it from flower to flower more effectively and do not destroy completely the flowers they visit.

A cool beetle pollination example

Beetle pollination is a very understudied topic in temperate regions such as Maryland, and we are still learning a lot about it. It is thus not surprising that the number of examples from our region is not super high. Let’s talk about one of them that happens to be relatively well-studied elsewhere but that also occurs in North America.

yellow and black soldier beetle on a magnolia flower — Beetles are considered some of the most important pollinators of species of the genus *Magnolia.* Here, a long-horned (Cerambycid) beetle on a *Magnolia grandiflora* flower. Photo: D. Hill (CC).

An example of beetle pollination of native plants that are also present in our region is that of Magnolia flowers. Although most of our knowledge on the pollination of this plant genus comes from studies done on species outside of North America, there are a couple of reports of floral visitors in several of our local species. From elsewhere, we know that these trees display flowers that appear to be particularly attractive to beetles: they are white, easily accessible, offer a lot of pollen, are fragrant, and in some cases even produce heat! In many of these species, the flowers appear to attract scarab beetles, which, once landed on the flowers, feed on the petals, mate, and then actively move between flowers and cross-pollinate. In North America, some studies like this one and this other one (in PDF) have found a wide variety of beetles attracted to our native species. Many of these beetles are very small and visit Magnolia flowers to feed on them, mate, and spend the night protected within the flowers.

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