With the huge losses of biodiversity that we are seeing across the world, a prominent example that became very close to people’s hearts is that of the large pollinator losses and the very important consequences that they could have on the well-being of our ecosystems and ourselves. In this context, a very large movement started seeking to “save the bees,” which has had a number of expected and unexpected consequences. One of the latter is the very significant increase in the adoption of honeybee hives by homeowners with little to no experience in honeybee husbandry, especially with the goal to “help bees” so they won’t go extinct. Although the goal of doing this is very genuine and well-intentioned, there are a number of complexities that come with this decision, which I would like to talk about in this post.
Are the bees dying?
The short answer is yes… kind of. Let me explain. As we mentioned in previous posts, there exists a very large diversity of bees (for example, only in Maryland there are about 400 native bee species!), and it is very clear that trends in biodiversity are negative for bees, as for many other groups of insects, plants and other animals. From that respect, we can say that many native bees are indeed dying, and it is key that actions are taken to provide more healthy habitat for them to survive.
That said, it is important to understand that honeybees are actually non-native livestock in our region (the group of bees that honeybees belong to are native to Eurasia and Africa, not to North America). Honeybees are managed and non-native insects that are reared by beekeepers to produce honey and other materials (e.g., wax, propolis). In places where honeybees are native, local peoples have been using their materials for generations, and in those regions, honeybees have not only been important from a production perspective, but also from a cultural one (read here to learn a bit more about some of these traditional systems).
As for all livestock, honeybees have health issues that need to be treated if they occur. For example, honeybees suffer from serious parasite and viral infections, appear to be negatively affected by certain pesticides applied to the plants they collect pollen and nectar from, and seem to also be affected by environmental stressors such as changes in the diversity of the landscape and the quality of the plants they feed on. All of this increases the real potential to reduce the health of colonies and, if left untreated, decimate them.
Again, the short answer is probably not. As I was saying above, honeybees are non-native to our region, so increasing their populations (for example, by increasing the number of hives) in our region is not likely to positively affect our suffering native species. For example, it has been shown in some studies that honeybees can be pretty competitive in the way they visit plants, displacing native species. Further, and especially if the honeybees are not properly managed (which is, unfortunately, the case for many new unexperienced beekeepers), they can become sick and spread diseases to native bees and other insects, also leading to increasing the pressures on these already-struggling native organisms.
Although we may love them with all our hearts, it is true that every one of our most beloved friends and family have sides that at times make us mad… and that’s no reason for us to love them less. I feel our relationship with pollinators and other beneficial insects is similar to that which we have with our loved ones: pollinators pollinate and play an important role in native plant reproduction and food production… and sometimes can become a nuisance if not properly managed. As for our loved ones, the fact that pollinators can become a nuisance shouldn’t stop us from supporting them; we just need to learn how to sustain our relationship while controlling its negative aspects. In today’s post we’ll talk about one pollinator in particular, with which our relationship can sometimes become complicated. Let’s talk about carpenter bees.
What are carpenter bees?
In our area, carpenter bees are large bees belonging to the bee genus Xylocopa. If you enjoy being outdoors, I am pretty sure you have already seen them. A very common species in our region is the eastern carpenter bee, which is about the size of a bumblebee, has a “dot” on its back and dark wings, and when exposed to the sun, has a shiny abdomen. These bees are very common in our area, and are very regular floral visitors of many ornamental and food-producing plants.
The eastern carpenter bee (left), a native to the mid-Atlantic, has a shiny abdomen, while bumblebees (right) have fuzzy and hairy abdomens. Photos: J. Gallagher, Wikimedia: R. Hodnett.
Because they are about the same size as bumblebees, carpenter bees are often confused with them. To differentiate them, a look at their abdomen will quickly allow us to know who’s who; carpenter bees have shiny abdomens, while bumblebees have very fuzzy and hairy abdomens.
The life cycle of a carpenter bees
It’s not random that carpenter bees are called that way. Their life cycle is tightly linked to wood, in which females dig holes to build their nests. Carpenter bees have impressive mandibles that they can use to chew soft wood to dig galleries in it. Although they may seem impressive, these are peaceful bees that sting only if physically and aggressively disturbed. In the spring, males of these bees establish and defend their territories, a strategy that will win them a female to mate with. During this defense, they “chase away” other males but also people who may be close to what they consider their spaces. These males are harmless, however, since they have no stingers and thus can’t sting.
Life cycle of a carpenter bee. Photo: NC State Extension.
The life cycle of these bees goes hand-in-hand with the season. In the early spring the hibernating adults emerge, mate, and the females build their nests in the wood. These nests consist of galleries, at the end of which the females lay eggs and store food (nectar and pollen) for the developing larva. The larvae develop throughout the spring and summer, and by the end of the summer emerge as adults. These adults are the carpenter bees we usually see flying in the early fall. Once the weather starts becoming chillier, at the beginning of the winter, these adults return to some of the cavities and overwinter there, emerging the following spring, to restart the cycle.
Why can carpenter bees become a nuisance?
As we saw above, carpenter bees nest in wood. If a house or any structure is built of wood, they may pick it to build their nests. When this happens, these bees have the potential to affect the integrity of our wooden buildings. So, we see that while these bees are very important pollinators native to our region, this particular aspect is the one that can be problematic in our relationship with them. The good news is that there are solutions for this!
Carpenter bees nest in wood, which sometimes can be a part of human buildings. Knowing how to proactively protect wooden structures is the best way to manage this helpful native pollinator, while protecting our buildings. Photo: H. Jacoba.
If there are no nests yet in the wood
The best solution is of course not the reactive, but the proactive one. If we have important wood structures that we don’t want to see occupied by these bees, the best we can do is first to use hardwood (which these bees tend to dislike) and/or to treat the wood. The treatment consists in painting or varnishing the wood, which will deter the adults from nesting in it. A very good treatment is coating the wood with almond oil in the spring, which will deter the bees from choosing that section to nest.
Another proactive action that can be taken along with wood staining is to distract the bees from the wood that we want to protect. To do this, one can use pieces of wood that one may not be interested in keeping, and displaying them in other parts of the open spaces so that females choose to nest in those surfaces instead of in the wood we want to protect. Besides protecting the wood, this also allows us to support these important native pollinators from our region, all while reducing the potential negative impacts on our buildings.
If bees are already established in the wood
If carpenter bees are already established, there are several options. First, if the number of nests is really low, and if the structure can be removed and replaced, then this should be done and the new wood structure should be stained to protect it. If possible, the piece of wood that is removed can then be placed elsewhere in the green spaces around the property, which will provide nesting resources for this pollinator, and will simultaneously protect the house and support native pollinators.
Carpenter bees can sometimes establish many nests in structural materials. If this affects the integrity of the building, more extreme actions may be needed. Photo: JoeyZ51.
If the piece of wood can’t be removed and, in particular, if the nests appear to jeopardize the integrity of the building, a more radical action should be taken. In that case, the use of insecticides can be considered. If this path is taken, it is important to not perform insecticide applications without proper knowledge, meaning that this should be done by an expert applicator. This point is really important, because non-targeted and improper insecticide treatments can lead to a lower efficiency of the treatment on the carpenter bees, and the death of other non-target beneficial insects (e.g., other bees, beneficial pest control insects, etc.) that may become in contact with the treated region.
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!
Spring is well-established and many flowers have already started to bloom. In my garden, I have seen several sizes and shapes of insects visiting flowers, going from small flower flies to butterflies, to very tiny and shiny, fuzzy large, and very large bees. And with all these flying organisms starting to come around us, I thought today would be a really good time to introduce you to some really cool bees that are very common in our area: the leaf-cutter bees!
What are leaf-cutter bees?
As its name suggests, these are solitary bees known to cut leaves (now you may be thinking, “duh, I could have guessed that without a blog post”, but bear with me!). These bees belong to a very large family of bees called Megachilidae, which is present on all continents except Antarctica and well-represented in our region.
Like most solitary bees, the female of leaf-cutter bees builds nests with small brood cells, in each of which a food provision is left and one egg laid. And this is where the “leaf-cutter” name comes from. When building their nests, many of these females line their brood cells with specific materials, in particular plant tissues. In fact, many of the species are known to cut leaves and/or petals to line their nests, using them to stabilize the brood cells, and likely to provide protection to the larva and the food provisions. In a fascinating way, it is suspected that these bees are able to exploit the antimicrobial effects of certain compounds present in these flowers and leaves, indirectly using them to protect their offspring until they finish their development in the nests.
If you ever saw neat and relatively large holes that seem to suddenly pop up on certain plants in your green spaces, it is very likely that they were made by some of these bees that may be nesting close to you! If you keep an eye out on those plants, it is very likely that you will end up seeing these busy bees carefully cutting, then rolling, and finally flying away with the neat plant circles!
Female leaf-cutter bee cutting a leaf
Megachilids are known for cutting leaves that they use to line the brood cells of their nest. Note that here the nest is in a soil mound and each brood cell is completely covered with leaves but capped and separate from the neighboring cells. In this nest, each cell contains one egg. Photo: E. Soh.
Looking out my window, as the ground is covered with snow and I am getting ready for another snowstorm coming tonight, it seems ironic that I have been spending many hours these days ordering seeds and planning my garden. While I am thankful that the winter brings some rest to the soil in my garden, planning this season brings me happy memories of the scents and buzzes in my yard during the growing days… which reminds me that I should also plan for my little buzzing pollinator friends when I plan what to grow this season. In today’s blog, I want to chat about how we can plan for many types of pollinators, with a special focus on planning for specialists and not just for generalist pollinators.
Specialist pollinators – never heard of them?
As we mentioned in a previous post, pollinators visit plants to feed on nectar and/or to collect pollen to feed themselves or their offspring. However, pollen is not just there for pollinators to feed on; pollen is central to plant reproduction, so plants tend to make it both attractive to pollinators but hard to digest. For this reason, and in order to be able to properly digest the pollen, pollinators are often specialized in their pollen choices. This is because being able to digest the compounds that plants add to their pollen to make them hard to eat requires some level of adaptation, which often involves a trade-off with the ability to eat anything. There are, of course, many levels of specialization, and, while many pollinators feed on many plant families, others are more specialized than that, and feed on only specific plant genera or even species! For us gardeners, this means that if we want to support many different pollinators, we need to make sure that we are also providing for those very specialized pollinators as well!
Luckily for us, the floral choices and pollen specialization is known to some extent for Maryland and Eastern USA bees (see this site to learn more). For this reason, we know that many specialized bees in our region are also rare or uncommon… another reason to try to provide resources for them!
Who are pollen specialists in our region?
Many known pollen specialist bees in our region belong to bee genera Andrena, Colletes, Osmia, and Melissodes, which have many species considered rare or uncommon in Maryland and Mid-Atlantic.
The sun and the warm(er) days are back! Oh gosh, it felt like forever! And now, of course, I am feeling like I have to get out there and start doing stuff outdoors! And because I love the little creatures, one of the things I want to do is make sure that this year my garden becomes a pollinator’s paradise. If you are in the same boat as me, come along and let’s talk about how to make our gardens inviting to pollinators!
Like us, pollinators need food and a place to live
We hear a lot about pollinators and the plants we can grow to help them. And it is true, to live and thrive pollinators need food, and that food usually comes from plants. Indeed, to sustain pollinators, it is key that we provide food for them. However, we often forget that they need something else to thrive: a place to live! And because there are SO MANY types of pollinators, let’s for this one time focus on only one group, the bees!
Even though many people think only of honeybees when we talk about bees, most bees do not live in colonies like honeybees do, and are in fact solitary. Solitary bees are indeed the vast majority of bees. In Maryland we have about 400 different species of them, going from tiny to very large. Check out this awesome free book about bees from our region.
Unlike honeybees, each of these wild bee species has different nesting requirements, and many of them will nest readily close to our houses if they find the right conditions. Here I will give you some pointers on how to create those conditions to not only attract bees with flowers, but also help them live close to your garden.
How do wild bees live?
Unlike honeybees which lay eggs throughout the growing season, wild bees usually lay eggs only at certain times of the year, meaning that their life cycle is different from that of honeybees. Most solitary bees in fact lay eggs at only one point throughout the growing season (for example, only in the spring, summer, or fall).
Wild bees lay eggs in their nests and leave food to them. When the larvae hatch they find the food and can finish their development in the absence of the mother. Photo: USDA ARS.
Whenever they are ready to lay eggs, bee mothers start looking for a place to nest, and it is only during this time that they will be building their nests. Once the eggs are laid, the mother leaves and those eggs stay in the nest along with some food (usually pollen mixed with some nectar). After hatching, the larvae eat the food the mother left for them, and they continue feeding and growing until they are ready to leave the nest as adults, usually the following year. This means that for most bees there is no or very little maternal care of the offspring, and most of the time spent in a bee’s life is as a larva, growing and getting ready for the “outside” world.
Where do wild bees live and how can I help them nest?
Wild bees have a variety of nesting preferences. While some nest in the ground, others dig holes in wood, use already-existing cavities, or parasitize other bees’ nests by consuming the reserves of their hosts (yeah, bees can be sneaky like that!). Understanding this is important, because depending on the resources we provide for nesting, different species will be attracted to our gardens.
Keep some ground undisturbed – Ground-nesting bees
The green sweat bees are very common in Maryland and can be seen often digging on bare ground and visiting flowers. Photos: J. Gallagher; Ilexin.
If you would like to support these bees in your garden, you can make sure to leave some of your garden soil undisturbed or bare. If you do this, you will realize that many bees will be attracted to that section, and if you pay attention, you will realize that many are actually coming in and out of the ground! These are your ground-nesting bees! In Maryland, some ground-nesting bees that you may have seen visiting flowers are the small and shiny green sweat bees.
Leave some wood in your yard – Carpenter bees
The large carpenter bees nest in shallow galleries they excavate in soft wood. Photo: Missouri Department of Conservation.
In our region, these bees are represented by the very large shiny carpenter bees of the genus Xylocopa. These bees have strong mandibles they use to excavate soft wood in order to build their nests inside. If you would like to attract these bees to your garden, make sure to leave relatively large branches and logs available for them to nest in. For this, you can turn a corner of your yard a bit wilder, and at the same time, leave branches there to allow other beneficial organisms to establish in your garden.
Bee hotels! – Cavity-nesting bees
Cavity-nesting bees are attracted to bee hotels. Here we have a particularly elaborate bee hotel; you can go simpler at first and then evolve into this if you’re just starting. Photos: M. Lankford; Piqsels.
Unlike carpenter or ground-nesting bees, these bees do not create the cavities, but rather use those that already exist. This is the group of bees that is attracted to those cute bee hotels one can build or buy. A natural option for supporting these bees is also by not cutting down to the ground the hollow stems of some plants at the end of the season. Many bees nest within these stems, and will die if they are chopped-off during the winter. Species in this group of bees nest in the spring, summer, or fall. For this reason, if one wanted to use bee hotels to attract these bees, one should establish them early in the spring.
There are a multitude of types of bee hotels, with some involving little tubes that can be removed, holes drilled into wood, a collection of small hollow twigs and branches, paper rolls, etc. Check out this site to see many options. Independently of the type of bee hotel you want to use, something important is to make sure that you keep the cavities clean for the bees to develop in healthy conditions. Failing to do so may actually harm the bees we are trying to support, because they may continue to be attracted to the nesting site we are providing but may eventually become sick and die because the place was unhealthy.
Now it’s our turn!
I really love watching bees build their nests, independently of what they look like. Maybe I’m just nosy, or maybe this is really why I’m a biologist, but that peek into these little animals’ lives makes me feel connected to them and keeps me in awe at how wonderfully diverse and fascinating life can be. When you are planning your garden this year, I invite you to consider the flowers for your bees, but also count in where you plan to have them live! And then, later in the season, go check those places out; I’m sure you won’t be disappointed!
By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.
New! Anahí is starting 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!
