Lonely Bees: The Misunderstanding of Solitary Bees

Bees are often upheld as the pinnacle of cooperation. We speak of bees as enlightened individuals who do what’s best for their colony despite the sacrifice and cost to themselves. Who’s ever even heard of a solitary bee? To most people, bees live in hives with thousands of other bees and make honey, and that is that. Honey bees have become the mascot of all bees, overshadowing the majority of bees and their importance to humanity despite not offering us any sweet substances. This couldn’t be more opposite of what goes on in the bee world. Bees that live in colonies are the exception rather than the rule. Most bees don’t make honey. 11 species of bees make honey out of nearly 21,000 species worldwide. That’s 0.0005% of bees!

It’s important to note that about 90% of bee species are solitary. These solitary bees are critical pollinators in various ecosystems and agricultural systems, often more efficient than honeybees in some contexts. Their diversity in nesting habits and solitary nature highlights the adaptability and evolutionary success of these bees in different environments. So without further ado, let’s introduce the real stars of the pollinator community!

The Solitary Bee

So it has been established that most bees don’t live in colonies. So where do they live? The majority of bees are ground nesters; they burrow into the ground and make little underground caves to lay their eggs. Each female is responsible for laying her own eggs, unlike honey bees where only the queen is responsible for baby-making. While the ground is home to most, some bees choose to live in hollowed-out stems of pithy plants, and some burrow into wood. Others prefer to leave the work to someone else and choose burrows made by other insects, usually beetles (this is because most bees don’t have strong enough mouthparts to chew through wood!). Some bees are even tricksters, and will sneak into the nest of another bee and lay her eggs on top! Let’s look at the life of a female ground-nesting bee.

Little Miss Solitary

The life of our solitary female bee starts when she emerges from the ground in spring. She was laid as an egg by mother bee the previous year and overwintered deep in the ground to keep from freezing. She may have had several sisters and brothers, but she won’t get to know them.

Her first job of the season is to find a mate. She’s also a little hungry, and, luckily, the male bees usually hang around flowers waiting for the ladies to fly by. She will mate with only one male, whereas the males are a bit more promiscuous. Once she has what she needs from the male to fertilize her eggs, she can store the sperm for life.

Now it’s time to get provisioning! She will look for a good neighborhood to lay her eggs. Once she finds something up to her standards, she will excavate her new home and make trip after trip to flowers, bringing back loads of pollen and nectar to place in every cell she makes. Each “cell” is its own little branch in the cave system that Miss Bee has dug. Combining the nectar and pollen to make a little ball, she places one in every cell, lays her egg on top, and closes off the entrance to the cell. Most solitary bees have one generation of offspring a year. Our lady bee will stay with her babies (brood), continuing to add cells and provision them until the season is over. With her babies secure, she will die as the days get colder and shorter.

Each species has its preferences for how they build, provision, and care for their eggs. They use different materials to make their nests in, they provision it differently, and they care for their eggs differently.

Mister Solitary Bee

The males live a much different lifestyle than their male honey bee counterparts and a much better one at that. The males within a honey bee colony live a rather silver-spoon lifestyle for a short while. Their one job is to mate, so until then, they get to hang out in the hive and eat honey duty-free. Their pampered ways come to a brutal end upon mating with a queen as their insides are ripped out of their bodies (much like the sting of the female bees). Not so with the solitary male. Although he is responsible for collecting his own food, he will mate to see another day. In fact, solitary male bees mate with as many females as possible throughout their lives. Because of this gigolo lifestyle, they don’t sleep in the nest with the solitary female. They instead spend their nights dozing on flowers.

The Sting

I mentioned before the comparison between the male bees’ genitals and the female’s sting, and it is interesting why this is the case. A female’s stinger resides in the same location as their ovipositor, their egg-laying organ. The close contact of the ovipositor and stinger means that when a female decides to sting, important organs are ripped out along with the stinger, leading to her demise. Males, solitary or not, have no egg-laying organ and therefore no stinger. Some males make aggressive displays and will sometimes defend flowers for the sake of the females they hope to mate with. Not to worry, without a stinger, these displays are only for show! The bee equivalent of revving the engine of their huge truck 🙂 Females rarely make defensive displays; they are far too busy gathering food for their babes.

Types of Sociality in Bees

The solitary bee has been the focus so far. I want to take a minute to highlight the other types of sociality in bees because it’s incredibly diverse and interesting. Some families of bees have a range of sociality, like in the case of the sweat bees (Family Halictidae).

Eusociality: This is the highest level of social organization, found in species like the Western honeybee (Apis mellifera) and bumblebees (Bombus spp.).

Eusocial bees have a reproductive division of labor, overlapping generations, and cooperative brood care. These colonies are typically structured with a queen and sterile worker bees. Ants and some types of wasps are also eusocial.

Subsociality: Some bees exhibit subsocial behaviors where a mother provides care for her offspring but does not live in complex colonies. For example, the carpenter bees (Xylocopa spp.) exhibit this behavior, where the mother builds a nest and tends to her young but does not create large colonies.

Communal Bees: Communal bees, like the alkali bee (Nomia melanderi), share a nesting site but do not have queens or workers.

Each female bee builds and provisions her own nest, but they may live in the same area to increase security or resource efficiency. It is similar to living in an apartment complex where each bee shares the common area, but they all have separate entrances and living quarters.

Solitary Bees: The majority of bee species are solitary. Each female builds and provisions her nest independently, often laying a single egg per chamber.

These ladies prefer the single life and won’t be around to watch their babes hatch. Examples include the leafcutter bees (Megachile spp.) and mason bees (Osmia spp.). These bees do not live in colonies or exhibit cooperative brood care.

Nesting Habits of Solitary Bees

Solitary bees display a variety of nesting strategies. Some build nests in the ground, such as sweat bees (Halictidae), while others, like mason bees, nest in pre-existing cavities or construct nests using mud or leaves. Many solitary bees prefer to nest in aggregations, where numerous nests are clustered closely but without cooperative interaction between individuals. These aggregations provide protection and efficient resource use but lack the structured division of labor seen in eusocial species.

Identifying Nesting Sites

When identifying bee nests, it’s essential to consider both the species and the environment. Ground-nesting bees, such as mining bees (Andrena spp.) and sweat bees (Halictidae), tend to nest in areas with well-drained, sandy soil in sunny, open spaces with minimal vegetation. You’ll often find their nests as small mounds of loose soil at the entrance. In contrast, cavity-nesting bees like mason bees (Osmia spp.) prefer pre-existing holes in wood, stems, or rock crevices, making urban gardens, forests, and woodlands common nesting sites. These bees thrive in temperate climates with abundant flowers for pollen and nectar during the spring and summer.

Nests are more likely to appear where the surrounding habitat supports a rich diversity of plants and favorable weather conditions for foraging and brood rearing. Weather also plays a role, as consistent, mild temperatures and minimal flooding ensure the nests remain intact for the bee larvae to develop.

Solitary bees are fascinating and if I’ve left you wanting to track some down on your own, NC State has an extension program with a fabulous article on examples of habitats for solitary bees that you can check out here. Familiarize yourself with the kinds of bees found in your area and try hunting some down to see for yourself.