Exploring the Fascinating World of Ground Nesting Bees

Introduction

Jordan: Where do we find these amazing sites that support, you know, thousands, tens of thousands, hundreds of thousands, into the millions of bees? I mean, there are some places out there that are acres of ground nesting bees. And we don’t know how long they’ve been there. We don’t know how many bees are there, but it’s in the many millions.

Shannon: Nature isn’t just “out there” in some pristine, far-off location. It’s all around us, including right outside our doors.

Hi, my name is Shannon Trimboli and I help busy homeowners in the eastern U.S. create thriving backyard ecosystems they can enjoy and be proud of.

Welcome to the Backyard Ecology podcast.

Welcome

Shannon: In today’s episode, we’re talking with Dr. Jordan Kueneman about ground nesting bees, which represent approximately 70% of our native bee species and have fascinating life histories but often go unnoticed because they spend most of their lives underground.

Hi, Jordan. Welcome to the podcast.

Jordan: Hi, thank you for having me. Excited to be here.

Shannon: I’m excited to have this conversation too.

What is a ground nesting bee?

Shannon: So, to get started, can you just give us a short overview about what we mean by the term ground nesting bees.

Jordan: Sure. Well, it is just like it sounds. So, we’re talking about bees that make their nest in the soil. And primarily we’re talking about solitary bees. So individual females that make a burrow and tumulus down into the ground. And then provision the future of their species, the next generation, underground.

Shannon: And just to be clear, because this is a concern that I hear from a lot of people when I talk to them about ground nesting bees, and I’m sure you get it too. We’re not talking about yellow jackets here.

Jordan: Right, we’re not talking about yellow jackets here. And we’re not usually talking about social bees. I mean, that’s sort of a big shift in people’s perspective of bees is that most bees are solitary. And they nest individually. And most bees nest in the ground.

Shannon: So that means it’s one female doing all the work, really. She’s building the nest.

Jordan: And she’s, uh, gathering all the resources for her offspring. So yeah, single mother, hard at work.

Shannon: Yes. You might have a lot of them in one location. But, the way I often describe it is that’s your neighborhood. That’s your subdivision.

Jordan: Yeah. We refer to those as bee aggregations. Um, and that’s primarily what I’m working on and what I’m fascinated in, is how do these bees form aggregations? Where do they form them? And why? And how do you get them to persist in the environment?

But that’s correct. You’ve got lots of individual bees making nests in the same location. So obviously they like that spot for a reason.

What sparked your interest in ground nesting bees?

Shannon: So, what got you interested in ground nesting bees?

Jordan: Wow. I mean, there’s a lot that keeps me interested in ground nesting bees. But how I got started studying ground nesting bees was from a molecular microbial perspective. So, I actually came into the world of ground nesting bees interested in how bees use microbes to preserve their resources underground.

Shannon: That’s something that I’ve never really even thought about. That’s cool.

Jordan: Yeah, so you can imagine that, you know, a bee is out there collecting pollen and nectar. But they’re storing these resources, which are very sensitive and important, in an environment that’s damp often, that’s, you know, laden with fungi, and in an inhospitable environment to store food resources.

So, it was, uh, sort of starting down that path of, “How are they keeping these things preserved underground?” And from there, I started coming across aggregations of bees. Because for my research on the microbiome of the brood cell, which is the chamber that they create underground, and they provision their resources in and lay an egg on.

Um, when I started trying to gather those types of samples, I needed to get multiples from the same species at the same time. So, I really needed to find an aggregation of nesting bees. And once I found what an aggregation was, I was blown away.

Shannon: Yes, they are extremely fun to watch when you see them.

Not all bees nest defend their nests or “hives“

Jordan: They’re mesmerizing, aren’t they? Like you, you can just be a part of their world because all these bees are very gentle, and they don’t really care that you’re there. And so, you can just be as close as you want and observe them going about their business in a way that I never thought possible. Um, you know, for bees.

Shannon: Yeah, because we always think of bees, we think of honey bees where you’ve got those huge hives. They’ve got a lot of resources to defend, and they will defend them.

Obviously. Anybody would. Um, so it makes sense that the bees would too. But this is a very, very different situation with these solitary ground nest bees.

Jordan: Entirely different. They’re going about their own business. There isn’t this urge to defend. You know, they’re more worried about getting to their nest and back out to forage again so that they can create a new chamber for another bee and they try to maximize their time that way.

They don’t even really defend against the other bee parasites or other parasites that are in their environment. I mean, they might a little, like if they recognize them, but they’re often too distracted and don’t seem to really care that much about parasites that are taking advantage of their hard work.

Shannon: Yeah, let’s come back to that because that’s something that people don’t think about a whole lot are parasites of bees. I mean, it’s just not even something that you think about.

Surprising unknowns

Jordan: Yeah. Well, I mean, you have to observe these aggregations and people don’t know really how present they are in the environment. It’s, it’s sort of an open question, right?

We’re trying our best at this moment, and in this work that we’re doing with Project Ground Nesting Bee, to map these aggregations and then follow them through time using community scientists, give us information as to what’s the size of this aggregation. Who’s there? Um, what does it look like from year to year? What are the attributes of that environment that they’re nesting in that make that so important to them?

Shannon: Right, because we assume that we know most things about the environment, and especially the common things that we might find anywhere.

Jordan: Right.

Shannon: And we don’t. There’s a lot of things that we don’t know.

Jordan: I feel like that’s just typical of entomology in general. There’s so much we don’t know. I mean, there’s, yeah, overlooked species, understanding their distributions, their relationships. It’s largely unknown, surprisingly.

Shannon: Yeah, it’s you don’t know what you don’t know, and then once you start learning what you don’t know, it’s like, oh my gosh, I know nothing. Um, we know nothing.

Jordan: Well, that’s why I like this project so much, because it gives people the opportunity to have a personal experience with bees in a way that they couldn’t before. In the same way that I did when I came to the realization, “Wow, this is very important. I want to get out there. I want to learn more about these bees,”

Because you can visit these aggregation sites. Um, and they’re going to be there year after year, if they’re maintained in a safe way, and you can just go experience them and you know where they’re going to be. You know when they’re going to be. And once you learn where they are in the environment, there’s different species to observe.

There’s interesting biology in your backyard that you haven’t yet experienced.

Ground nesting bee diversity

Shannon: There’s like 70 percent of our native bees are ground nesters.

Jordan: That’s correct. And in the U. S., we have around 4,000 species of native bees and 20,000 worldwide. So that’s a lot of species that are going under the radar that are not really top of mind for folks when they’re thinking about bees.

But also, aren’t really included in our discussions about how we should be managing the environment, how do we create sustainable ecosystems, and maintain pollinators and diverse pollinators in our environment.

So that’s part of this, is figuring out where these amazing sites are that support the birth of our native bees. And how do we maintain those in the environment?

Shannon: Exactly. And, you said 4,000 in the U. S. Do some parts of the U. S. have more ground nesting bee species than other parts? Or how does that kind of play out? Or do we know?

Jordan: Well, we don’t know all the details there, but certainly there are areas that are more diverse than others and there are environment types that seem to favor ground nesting over others. Um, and we’re starting to learn where these large aggregations are more likely to be found.

So that’s part of the goal – where do we find the diversity of ground nesting bees? Where do we find these amazing sites that support, you know, thousands, tens of thousands, hundreds of thousands into the millions of bees? I mean, there are some places out there that are acres of ground nesting bees.

And we don’t know how long they’ve been there. We don’t know how many bees are there, but it’s in the many millions. And so that’s just a tremendous resource in the landscape. It’s a tremendous biological event that occurs every year.

It would be wonderful to learn more about this across the landscape and to get people engaged in understanding their biology, reporting on where they are and then protecting them in the landscape.

Where to find ground nesting bees

Shannon: And can you give us some ideas of just generally, like, what types of areas do they like the most? Where do you find the most diversity? Some of that, what we know about it, or think we know about it.

Jordan: Yeah, that’s, that’s to be, you know, determined, really. I mean, where we see them the most, and where we get these very large aggregations are often in south facing mowed lawns, cemeteries, uh, places where there’s been management that’s been consistent over a long time.

But that has a lot to do with certain types of bees that are able, that are willing, to form these large aggregations. That has to do with our ability to find them.

So sometimes they’re in the forest or they’re in areas that had been flooded previously. And so sometimes we wouldn’t come across those, but that’s what we’re trying to figure out.

I mean, this project is about locating large aggregations and determining, you know, why bees nest where they do, but it’s also, uh, wants to capture the more rare species and species that are individually nesting that aren’t in aggregations, and get a sense of where they nest. And those are big, open questions as to where they nest and why.

Shannon: I know, on our property, we’ve got an area that I find them in every March, early March / late February. It’s a north facing slope, sort of sandy clay soil. It’s a loamy clay with some sand mixed in. And then, it’s on an old roadbed, tractor roadbed, actually, um, within a forested area.

And they are out for a week, maybe two weeks, usually a little closer to a week. I mean, if you don’t see them and go out and photograph them and enjoy them, then it’s done. You’ll see nothing afterwards, but yeah, so, we get that every year.

Jordan: So, was it was it because of the soil type? Was it because of the soil type and it was compressed, uh, by a tractor at some point? Like what in the history of that site led to it being an ideal place for bees to then continue to come back to and reproduce in year after year?

I mean, those are some of the outstanding questions. That’s what we’re trying to figure out. How do we learn what they want and maybe how do we make sure we include it in our landscapes?

Shannon: Yes.

How to identify ground nesting bees

Shannon: Shannon: So one of the things that I’ve always been kind of curious about with our bees is, what species are they? Because like you said, there’s lots of different species here.

And so do you have tips for how to go about identifying them that a normal person could do without having to try and catch them and stuff like that. Just looking at them. Or can you?

Jordan: Yeah. Well, I mean, often people want to immediately jump to, “What is this bee species?” and largely that takes a taxonomic expert with a microscope.

Um, but move up, you know, you can start with what is, “What is the family of bees?” Like bees are so diverse. So that’s a good place to start. Like, where’s the bee carrying its pollen? You know, what are some of the other physical attributes of this bee?

And then once you kind of learn some general traits of the family level, you can say, “Okay, what are the more prevalent genera of this bee and what are some of those attributes?” And so, you kind of need to start a little bit higher and move yourself to a point of understanding, uh, what bee you’re looking at.

And so it’s a bit tricky, but one place that we encourage you to start, especially if you’re observing a ground nesting bee is to add it onto our iNat project. It’s goal is to help figure out where these bees are nesting and who they are. And so then we, and many experts and people engaged in the iNat community, can provide some taxonomic resolution there.

And, if it’s a bee that we think, “Oh, this is very important. Let’s figure out more about it.” Then we can work directly with you, um, to try to understand your aggregation, in more depth.

But certainly, there are resources by state, right? I mean, people have broken this down, um, extension office, you know, people in your state, uh, often will have guides. Um, there are some general books, you know, Common Bees of the Northeast or Common Bees of the West.

Like there are places to kind of get just your foot in the door, but obviously it’s, um, it’s a bit involved.

Shannon: Yes, I’ve looked at some of the books and the field guides and stuff and I’m like.. I don’t know. I’m not getting something with it. It’s like, okay, it’s a ground nesting bee.

I mean, there’s some that I was like, “Oh, yeah, I know that one,” umm, bicolored sweat bee. That one’s the bright green. It’s got the white stripes. It’s like, okay, I can get that one.

Jordan: But then, you can take that and be like, “Oh, it’s metallic,” you know. “Oh, it has this,” “Oh, maybe it’s more likely Halictid,” and then go more directly there.

So, there are these traits, um, that if you learn a little bit about these higher levels of bees, you’re like, “Oh, okay. I know where to start looking in more detail.”

Shannon: It sounds like it’s like birds and like with plants and everything else. You start with one place and keep going down.

Jordan: And look at what they’re doing and where they’re doing it. Right. I mean, the fact that they’re nesting in the ground. You know, often people are unaware that there’s these whole behavior types of bees that generally has a taxonomic link, right? Like whether they’re nesting in reeds or stems or you know carving out a hole in some dead wood you know. Those are traits for different groups of bees.

Favorite ground nesting bee

Shannon: So do you have a favorite species or genera or family?

Jordan: Oh my gosh. I actually I do which is surprising. I generally try not to. Yeah, I like the Diphaglossine bees this is a special group of Colletid bees.

Bees that, first are very large and charismatic. They’re also generally found in South America, but there are some species that are found in Florida, um, Arizona, um, and they’re just a very unique bee.

They typically make a very deep nest, um, and their brood cells are, are large and they have cool physiology often they have like little caps. They might even have like little vents on them. They partition their food you know when the bee develops from there the excrement that goes below like they’re just sort of a really fascinating bee.

The main reason that, you know, I’m so excited about them and I’ve been pursuing them particularly is that their pollen provisions seem to be highly fermented. They have a unique odor. They have this smell of lactobacillus.

And so, what we’ve learned is from the two species that we’ve studied in detail is that they have monocultures of lactobacillus bacteria in their pollen provisions. And so, they just have this real specialized association. Um, and so that’s, that’s one group that I’m particularly fascinated in for a number of different reasons.

Shannon: They sound like they’d be fascinating just from the behavioral standpoint. And then also, I mean, that goes back to your microbial interest that really got you started to begin with too.

Jordan: Yeah. And they form large aggregations and they’re just, they’re large charismatic bees and they have these funny tongues that are like mops and they just, you know, they’re cool bees.

Observing aggregations

Shannon: Yeah. My bees are, my bees are interesting. They’re these little. I don’t know. They’re little fuzzy bees. It’s the best way I can describe them. But yeah, they’re really fun.

Jordan: So, this is what we want to encourage people to do is when they come across these aggregations in their backyards or favorite hiking trails or wherever they come across them is to take an up-close photo of the bee typically at the nest entrance.

It’s challenging. You got to have some patience. Or you can get the bee and the nest entrance separately and say, these occurred at the same place because you know, we want to see the bees so we can get a sense of who it is there, but we want to know where it was.

So, bees on flowers aren’t part of this project. Nest entrances are, right. So, where they’re actually going into the ground because it’s that location and the soil attributes underneath it that are the unknown.

Once you get that, you can upload it to the iNat project, Ground Nesting Bees, and then we can help you work on, you know, getting a rough identification and follow up with you if it’s a particularly important aggregation to be a part of other parts of the study.

Shannon: And I will say from experience, it definitely can take some patience to get the pictures. Because with mine, I mean, as soon as you move…

They’ll let you lay there. I mean, I lay there three feet from them, but if she’s starting to come out, as soon as you move, she’s like…. and runs back down inside and hides.

And I mean, it’ll be like five, 10 minutes again before she decides to start to peek out again. But then, if you catch it the right time, there’s others flying around you, so you’ve got other things to look at, but…

Jordan: And often I think you get them coming back. Um, coming back to their nests. And so there are some tricks. I mean, even to figure out like sometimes we’d put little plastic Dixie cups over a hole just to see who’s trying to leave or see who’s trying to come back.

Um, but yeah, when you’re trying to get that natural shot you can just lay there close to an entrance and not move and hopefully you’d get one that way.

But something that’s often good to do also is just to get like a video of the action of all the movement, um, and photos from a distance as well. So, we can get perspective as to what type of environment is this. You know, is this a grassland, is this a park where are we? You know, where have these bees chosen to nest?

When’s the best time to look for them?

Shannon: Well, I know like with my bees, it’s like I was saying before, it’s late February, early March, when we get that warm up. Um, about the time you start going out to look for the very first, earliest spring ephemeral wildflowers. Maybe even a little before that. But, that’s when we find them. It’s a week, maybe, that they’re out and flying.

So, when should people go look for them? Is it mostly late winter, early spring, more spring, summer?

Jordan: So like you mentioned, I mean, these bees are punctuated in the sense that their adult activities are a few weeks out of the year. So, in all the cases with these aggregations, the males will emerge first, and they’ll just kind of hover over the ground. And what they’re waiting for are females to emerge to mate with, and then the males will die, and the females will begin the process of provisioning for the next generation.

And so they’re timed with, you know, every bee species is timed with its emergence of a certain group, a certain suite of flowers that they associate with. And if they’re part of that early spring, often they’re going to the tops of trees that have begun to flower first.

Um, and so to back up and say, okay, well, each bee species is timed with a certain group of flowers. And flowers start in the spring and finish in the fall. That means you’ve got bees emerging from spring to fall, along that period that are timed with certain flower emergence. So that’s important to understand. So, you can find them at any time.

A lot of these bees that we think of that form these large aggregations, they’re typically the spring bees. So, they’re whenever spring is occurring in your place. So, in Florida, that may be February, um, in New York, where I am, you know, we get them, you know, end of March, um, April, mostly, and into May. So, some of ours last longer and they occur later, but it’s important to know that bees are emerging all the time, different species of bees.

Shannon: Which I guess that would help narrow down which species you’re talking about too, is when is it active.

Jordan: Yeah. When did you observe it? That’s a characteristic that we look at. When was this be active? And so that’s, fairly well known and within some range, right? Is it a, you know, it’s an early spring bee, is it a mid summer bee, is it a late summer bee? I mean, those are things that are understood better.

But one thing that’s very interesting about those early spring bees is that a lot of our high value crops, a lot of the fruits, you know, the cherries and the apples and a lot of these important fruit crops are early spring flowering trees. Right? And so, they’re biologically timed, with these early emerging bees.

Um, and so these bees that can, you know, fly in inclement weather and handle the colder temperatures and are evolved in that time frame are much better adapted to pollinating a lot of our food. And so, there’s a connection there that we need to start to appreciate and implement into our management of bees and of food production and so forth.

Shannon: That’s interesting, because I’ve always thought of the early ground nesting bees as being more pollen specialists, but I’m sure there’s generalists too.

Jordan: Mm hmm. Yeah. Plums, apricots, blueberries, strawberries, you know, anything coming out early in your environment is timed with these early spring bees. And so, there’s a connection there that we can work with.

Life cycle of ground nesting bees

Shannon: And so they’re active for a couple of weeks or so as adults…

Jordan: As adults, right? That’s the part that’s kind of fun for people to start opening up their appreciation of bees, is that they’re largely underground and they’re largely developing underground or in diapause waiting for their time to emerge.

Shannon: So yeah, most of their life cycle takes place underground and they may be underground as an egg, a pupa, a larva, um, I guess in some cases an adult bee.

Jordan: Yeah. Some bees will over winter, but you know, a lot of them, uh, will stop their development as a late larvae or as a pupae, and then they will emerge when the conditions are right and become a reproductive adult. And that period is much shorter than the rest of the time they spent developing. And so the health of our soils is very important to bees.

Shannon: Because that can take a year.

Jordan: That’s right. And some bees will do some bet hedging, so some individuals will emerge, you know, after two years, uh, some bees only emerge every five years, you know, depending upon when the right environmental conditions are. So, there’s a diversity of strategies, even as a ground nester.

Threats

Shannon: Well, okay, so we’ve talked about a couple of the threats to bees with soil health. I mean, anything that you’re doing to disturb the soil could be an issue.

Jordan: It can be, I mean, surface level disturbance doesn’t seem to bother them so much, but deeper disturbance obviously would remove their ability to nest in that area.

Um, and, you know, obviously the biggest threats to bees are insecticides, right? I mean, those are the ones that they just can’t tolerate. Um, and then, and then we’re learning more about bees tolerance of pesticides, um, you know, fungicides and bactericides and things like that, which can have negative effects on bees.

But the obvious one and the one that’s most relevant and immediately important is to, you know, limit and reduce use of insecticides because those don’t go away.

Managing for ground nesting bees

Shannon: So what can people do to help with either managing for bees, well, let’s start with that. What can they do around their own home to help to create the habitat, and maintain habitat, for these ground nesting bees?

Jordan: Well, that we don’t know of yet. I mean, we’re still trying to figure out where they nest and why, right?

But if you have them keep doing what you’re doing, right? Like if you’re, if you already know where an aggregation is. And maybe that’s nothing, right? Maybe that’s doing nothing. And that’s perfectly fine.

Maybe you are already doing a mowing routine that works for them. Right? And you can do that. But maybe you adjust it a little bit, like mow before they emerge in the morning or after they’ve mostly gone to bed. I mean, those are considerations. But obviously, whatever a person’s doing, if the aggregation is there, the bees are happy in that environment.

Um, you know, recommendations for bees, more diverse bees or other groups of bees include keeping stick piles around but those are just general. Um, those are also, you know, apply to all other insects, right? You know, keeping some leaf litter around, keeping a diverse environment around some areas that are disturbed and some areas that are not disturbed and just more of a diverse landscape that you would imagine could support more diverse life.

Uh, but with respect to ground nesting bees, I mean, they either like it there or they don’t. And so if they like it there, just enjoy them.

How to find them

Shannon: So, I guess we should say, how do you find ground nesting bees, or even know if you got them there?

Jordan: Yeah, so that’s why this project takes such a large group. That’s why we’re reaching out to your audience. That’s why we’re trying to communicate broadly. Because if I were just to head out and try to locate a ground nesting bee aggregation, I would have a very hard time doing that.

I’d probably start by looking in cemeteries, start by looking in parks, start by looking in, I don’t know, a university landscape that’s like, okay, these people are doing the same routine year after year. Um, I’d look for south facing slopes. I’d look for, you know, sandy soil types, right, but it’s very difficult.

But that’s the reason to reach out to a broad audience because it’s like you, you have one, right, that we just talked about, right? You know where one is, but that’s what it takes. It takes communicating with people, telling them what to look for, and then once they’ve seen it, they have an eye for it and they might see it again.

But it’s more luck whether it’s in your backyard or whether it’s a place that you frequent, like you may be walking through one of your favorite parks and be like, “Oh, I’ve seen them all over this part of this bike trail, or all over this part of the road. I didn’t know what those were.”

And so that’s what we’re looking for, are people’s sort of observations that they wouldn’t otherwise know were important, but that are.

Shannon: So the two things that I look for, and you might have other suggestions too, are one, where it looks like somebody’s taken one of the old fashioned number two pencils that we grew up writing with, shoved it into the ground, and kind of wriggled it around a little bit, and then maybe it has, like, ant crumbles, soil crumbles around, but they’re bigger than ants. So, the hole’s bigger and the crumbles are bigger, but it kind of looks like that. That’s what I find a lot of times.

Jordan: Yeah, that’s, that’s very common, especially for Colletids and you know, some bees don’t really make the mounds or at least when they’re starting a new one, they do, but they immediately kind of, you know, get dispersed.

But bees are wider than ants, right? So, you’re right that the, that these nest entrances, these holes in the ground are typically, uh, wider, but there are also very tiny bees too, and those are interesting.

So, one thing to also look for is just this hovering motion. Like, do you see, uh, insects kind of just moving over the ground? Like they’re waiting for something to emerge or like they’re looking for their entrance, you know?

And so you kind of get this, just this, you know, this observation of, “Oh, there’s a lot of insect activity. Okay. What, what’s going on here?”

And then either you might be looking at males kind of doing this hovering motion waiting for females, or you might start to realize that there are bees bringing pollen back. And so, you’re looking for an insect carrying pollen back into its hole. And that’s, that’s it. Once you found that you’ve got it.

Shannon: That’s the second thing I always look for. It seems like I see, and I guess it’s because the flight period of them is so short, that I often see the holes before I see the flights and the patterns of them.

Jordan: Right. Yes. So, you might go back to your aggregation a week earlier or two weeks earlier this year and say, “Okay, well, what I want to see is just the first emergence,” or “I want to see the males swarming,” or “I want to see mating,” because mating is also very, you know, fascinating to watch. And “I want to see the females provisioning.” So we come back, right.

So, you know, that period of time, which may feel like a week, you know, may actually be a couple weeks once you start at the beginning and watch till the end, right? Um, and so that’s really what we want people to do.

I mean, the iNaturalist project gives people the opportunity once observations have been made in parks or in public spaces to go to those and start to get a, you know, a sense and start to learn, “Oh, wow, this is really cool to observe. This is just an interesting biological event going on in my neighborhood, um, let’s check it out.”

And then once you have that search image, you’ll start to keep an eye for other aggregations or talk to people that’d be like, “Oh, I think I’ve got something going on.”

And so by word of mouth, hopefully we can spread the message that these are important observations. And only by collecting many of them do we start to get a profile, a sense for what bees are nesting where, and why.

Shannon: Right.

Project Ground Nesting Bee and how to get involved

Shannon: So, we’ve mentioned the citizen science project, the community science project, several times. Can you tell us a little bit about it? Who can participate? Let’s start there.

Jordan: Well, it’s open to anyone that has made an observation. That’s the starting point. So, what you want to do is, well, you can join the project, and we encourage you, because then you get updates as to what we’re finding. Um, and you can look on the iNat page and see where observations are in your, in your community, and that’s a great place to start.

But we really encourage you to join the project and to make an observation. Even at an aggregation that’s already existing, add new data there, because often there’s different species intermixed into that aggregation. Often there are parasites of those bees that are also bees, and we want to know those relationships.

Uh, so we want repeat observations and to encourage people to go back and to observe them and to learn more about their phenology. When did they emerge this year? Is their aggregation the same size it was last year?

So even without finding your own to begin with, there are ways for you to get involved and ways for you to help build the corpus of data and observations that allow us to make conclusions and understand those bees better.

And then take that further and communicate and find your own aggregations and start that process over so that you can start teaching people more locally what bees are doing. And then also that can wrap into how does this bee fit into the context of other nesting bees in a larger geographic space?

Shannon: That’s interesting because I’ve never really thought about there being multiple different species within the same aggregation. I always thought that it was just kind of everybody was the same species in there. Except for your parasites that come and go.

Jordan: Yeah, well, sometimes it is, and sometimes it’s not. I mean, we’re, we’re getting feedback from different aggregations where the area is actually sort of, you know, sectioned off like there’s an area that’s more dominant in one species, but right next to it, another species nesting. And so, they’re attracted to the same types of, uh, you know, requirements.

Maybe that has to do with the floral resources that are close. Maybe that has to do with the sand that’s available or the sandy loam or the soil types, um, you know, and that’s what we want to figure out, but it’s fascinating that they’re sort of living side by side, but in the same general area.

Shannon: That’s really interesting.

Jordan: It can be. Yeah, I believe that those would make really important places to conserve, right? If you can, if you can support a diverse group of bees and it’s a unique location, something that we ought to know about and keep around.

Shannon: And like you said, making those repeat observations can be really helpful too, especially year after year after year, because that’s something I need to do a little bit more of. And Anthony and I, my husband and I were talking about last year, was that we really need to start paying more attention to the size of our aggregation, because we both got the impression last year that it was smaller than it had been in the years before.

So, whether that was a one time thing, or I mean, we know the woods have gotten a little thicker there than they were when we first moved in when we first found the site. So, is it because now it’s getting too deep into the woods and we need to open it back up?

That is an area we want to open back up again. Um, that’s in the kind of long term plans for that area. But yeah, so there’s all these questions just on that one little section that we’ve got.

Jordan: And if they were there, but that habitats changing, maybe they’re moving someplace else close by. And so maybe if you can communicate with your neighbors or keep an eye around there, you might start to find, “Oh, this is the same species. Likely it’s from the same population and they’re shifting over here.”

That kind of stuff is fascinating. We don’t know anything about why bees pick up and move and when they do, where they go. So, part of the same, you know, realm of questions. Why do bees nest where they do? And how do we encourage them to nest where we might want them?

Um, and so, yeah, keep an eye on your aggregation. Go back there and map it out on, on Google Earth. Get yourself some boundaries to kind of see what kind of area are we talking about.

And then if you’re part of the project and it’s a site that we want to follow up with you on, we may send you some resources to do some collections and then you can send those materials back so we can get a better understanding as to why they’re nesting there and who’s nesting there.

Shannon: Because that’s one of the things that I’ve loved about community science projects forever and why I used to work with them so much is because one scientist or even a lab, a team like you’ve got, can’t be everywhere. So it allows everybody to be able to contribute and to help. And you get to do so much more because we’re all working together to do that.

Jordan: That’s right. It was never possible before you know, we had these platforms to integrate observations and the community to help provide taxonomic identities and the ability to communicate broadly so we can get people to add these into a group project. And I think that’s, that’s just a wonderful new way that we can approach caring for the pollinators in our landscape.

So I’m very, very, you know, excited by this work. And I love the fact that it brings in people from all backgrounds. I mean, we’ve got high school students out there collecting soil and we’ve got retired gardeners that are fascinated, right? Like just the whole, spread of folks that are making these observations are willing to engage and to learn often to learn about what’s going on in their backyard.

Shannon: Yes, exactly. And I mean, these aggregations are found everywhere. Well, in all kinds of different types of habitats and areas because like ours is in a wooded area. Um, I know other people have talked to me about finding them on the soccer field. Or, at a park or at the university or at the high school or wherever.

Jordan: Right. Exactly.

Shannon: Yeah, in the backyard. I know people talk to me about the backyard, having them in there.

Jordan: I mean, that’s what’s so good about, you know, we’re talking about the backyard ecology, right? And, being part of this community gives you the opportunity to learn, you know, you don’t have to be worried about what’s going on there. In fact, you could bring folks over to observe it and be like, “Check this out. Let’s watch these guys for a little bit and just be a part of another world.”

Shannon: Yeah, and because they’re solitary because they don’t have that heavy defense instinct. You can run around barefoot in there, and they’re going to fly away from you. They’re not going to sting you. I mean, like I said, I lay three feet from them, and they’re more afraid of me.

Jordan: They’re just doing their own thing, you know.

Understanding the potential size and age of aggregations

Shannon: So any interesting stories or observations that you’ve made?

Jordan: Well, I mean, we’ve just mapped out this community at our local cemetery here, the East Hill Cemetery. And estimated that we have a population of over 5 million solitary ground nesting bees. So there are places that we’re finding that are just incredibly dense with bees.

Um, and talking to the folks that are there, and when the cemetery was created, you get a sense that like, “Oh, this is at least, you know, it could be a 90 years old.” How much older could it have been? You know, there’s no information beyond that.

But, certain areas that may have been part of like a flood event, right? That like really changed the landscape. And then, you know, there hasn’t been a reforesting of that area. You know, those aggregations that occur in these interesting environments like that, you know, maybe there are hundreds of years.

And so, I don’t know, I’m fascinated by that. I want to try to figure out like how long have these bees really been there? How did they get to reach millions? And I want people to have the opportunity to go see those types of sites as well.

Shannon: Yes, that would be, oh my gosh, that would be amazing. My site’s like measured in feet. So, it’s a relatively small site. I doubt I’ve seen 100 bees flying at the same time frame there. I mean, usually in the 10s.

Jordan: But that fits right into our trying to understand like what makes an aggregation of a hundred or a thousand or hundreds of thousands, right? Like, what does it take? What is it in the environment for bees to have that level of success there?

Shannon: And to be able to understand that, and that’s why I love this project and the idea of it, because yeah, we can start answering those questions that we never could even think about finding the answers to before.

Jordan: It’s unique. And, the history and, you know, the backgrounds on the biology of ground nesting bees is largely been worked on by a handful of folks that have heard accounts of a bee being in a spot and they go to that spot and they write a detailed description of the nesting architecture, the biology. You know, and that’s only been done for a small percentage of the bee species that we have.

Um, and most of that’s done from a single site observation. So, you know, being able to draw conclusions across sites has never been an option before because we didn’t have a resource in order to compare.

So I’m excited to be able to look at questions that pertain to the species of different aggregation sizes across space and try to figure out, you know, what makes a successful, uh, nesting habitat for bees.

Shannon: Yeah. My brain’s like asking itself so many different questions right now that I know we don’t have the answers to. Because if this is where we’re at in the science, it’s like, “oh my gosh, then what about this? And what about this?” But we’ve got to get this basic part first.

Jordan: Yeah. Yeah, build the network first and then, and we’re working on creating the tools to address the questions that we have while we’re starting to get the data in. So hopefully, after a few years or as we build this project out, we can learn a lot about why bees nest where they do.

Shannon: Which will be really exciting and then lead to even more questions that we can ask.

Jordan: Yes, absolutely.

Parasites

Shannon: So, we talked about the parasites of the bees real briefly, tell me a little bit more about those.

Jordan: Well, I mean, there’s two groups of parasites that I would sort of start with, right? There are the bee parasites. So, these are what I’m calling, you know, the deadly relatives.

Um, but those interactions are just being researched now and how these parasite bees, they form very close relationships, right? So we don’t know exactly, but, you know, we think of them as sort of being paired up with a host.

Obviously there might be some ability for parasitic bees to parasitize multiple species, but generally speaking, they’re sort of got these close relationships with host bees. Um, to the point where they may even mimic certain aspects of the host bee or they do function in ways that allow them to be close to those host bees without eliciting a response. And so that’s pretty fascinating.

Um, and then there are all the other parasites of bees, right? So, those are typically your beetles and certain wasps and, um, different flies. So these are whole groups of parasites that are specializing on bees. And, you know, that nests in different environments, but many of which nest in the ground. So that’s the whole ecosystem going on, living off of the work of these bees.

Shannon: Yes. And the parasites have parasites of their own. So, I mean, it just keeps spiraling.

Jordan: It just keeps going. You’re right. They do. Yup. No one escapes but those relationships I think are also interesting to understand because a high source of mortality for the host bees is parasitism, but they have to reach an equilibrium.

So, trying to understand who’s there and what they’re doing and how these relationships take place over space. Like, is it always the same parasites afflicting the same species, or is it a different suite? Um, are there sort of shared enemies or are they always your own personal enemy?

Shannon: Again, so many questions there that could be asked that we’re not in a place to start answering too many of them yet.

Jordan: No, but it’s good to consider those, right? And to like, you can take observations of the bee parasites for sure. Um, but you could take observations and include them in a bee observation and be like, okay, we’re seeing these beetles around here and seeing this.

You know, that kind of stuff can help as long as you have an idea that it’s interacting with that nesting bee. But we can get that information in more detail using other sampling methods. You know, once we know that the aggravation is a stable one and one that we want to study in more detail.

Shannon: And like for the bee parasites, if they look semi similar to the bees that are going in and out anyway. Then, I may not notice that, wait a minute, I’ve got two different types of bees going in and out here.

Jordan: They generally look fairly different. They don’t look the same, but they don’t often elicit much of a response. I mean, obviously, if it’s going into the same hole, like, you would you try to run anyone off. But they’re just kind of swarming in the swarm together.

And often they’ll, you know, there’s ones that are called blood bees, and they’re definitely more red, or like a red abdomen, and there’s ones, you know, that have more yellow, um, that are more yellow banded. So they look quite distinct.

Shannon: That’s helpful.

Jordan: What they do is they lay an egg, onto the pollen ball that the female’s prepared, and it hatches, and it gobbles up the resources, but it also decapitates, or otherwise kills the host developing bee, and gobbles it up too, uh, so it’s pretty brutal.

Shannon: Yes, there’s some really cool behavior once you really get into ground nesting bees and digging into it. I mean, really cool.

I’ve always thought they were fascinating since I learned about them. I mean, for a long time, I didn’t even know ground nesting bees existed, because bees are bees, right? No, not at all.

Jordan: Yeah, exactly. I mean with bees, you know, you have different foraging and host plant uses, right? You have these generalists we mentioned, you have these specialists, um, you have some bees that utilize oils from flowers. So there’s just some really cool stuff there.

Um, even the architecture related to their nesting is fascinating. So some bees will use these plugs or close their holes. Some bees are working really hard to create these linings that keep their tunnels open. Some bees make these cellophane bags to put their provisions in. So that’s really fascinating.

So there’s cool behaviors of bees, um, that are important. But there’s a lot to learn.

Importance of studying ground nesting bees

Shannon: Yes, I mean, we could go for hours and hours and hours just talking about ground nesting bees in general, and then go into the different families of them.

Jordan: There’s a lot. There’s a lot to go into, and it’s, you know, one of the least studied because they’re hard to find. You know, being able to find where they nest is a limitation to learning about their biology. So that’s what we’re focused on.

Shannon: And that’s one of the things that this project is going to help out so much with and why I really encourage our listeners to get involved and to make these observations and submit them, because that’s an important part too.

We’ve got to share what we’re finding and submit what we’re finding because it can make such a difference because we don’t know a lot about ground nesting bees in general, much less specifics about a family or a genera or a species.

Jordan: Yeah. And if we want to maintain diverse pollinators in our environment, which is, you know, paramount to maintaining diverse flowers in our environment. Um, and just healthy ecosystems in general, then this is a good starting point.

I mean, where they nest and why is, is just as important as making sure they have food out there to collect, but it’s often overlooked.

Shannon: Right. We focus on planting pretty flowers or pretty trees and we forget about all the other things that an animal needs or an organism of any kind needs in order to be able to survive.

Jordan: That’s right.

Resources

Jordan: Well, together we can make a difference on studying ground nesting bees.

And please, join the iNat project that’s called Ground Nesting Bees and follow us on Instagram. So you see some amazing photos and get tips on how to find bees and tips on how to take good photos.

And then for general information, there’s always G N B E E dot O R G where um, we’ll be updating it, uh, soon, but it’s a place to kind of get an overview and to see some of the research products that are coming out. So, we are publishing sort of detailed studies on ground nesting bees as, as we can that’s stemming from this work and acknowledging the contributions of this community.

Shannon: And I will definitely provide links for all those resources that you just mentioned so it’ll be real easy for people to find them and be able to participate.

Well, thank you so much for being a guest on the Backyard Ecology Podcast and for sharing your knowledge of ground nesting bees with us. This has been so much fun.

Jordan: And thank you for having me. And this has been wonderful for me as well. It’s always good to communicate about bees.

Shannon: And I hope that all of our listeners will keep an eye out for ground nesting bees this year and report any that you see to the Ground Nesting Bee Project so that we can continue learning about these fascinating insects.

Also, if you would like a free checklist of tips on how to identify ground nesting bees that I pulled together from this conversation, just go to the episode webpage and scroll down to the Bonus Content heading.

As always, I want to thank our Patrons and other financial supporters who go above and beyond to help us produce free content focused on creating thriving ecosystems and enjoying the nature in your backyard.