If I asked you to picture bees, there is a 100% chance you would imagine honeybees in wooden hives or bumblebees buzzing around flowers. Few realize that the world of bees is vast. And ground bees make up the majority of bee diversity worldwide.
Of the more than 20,000 known species, roughly 70% nest underground. Not only abundant, these species are also essential to supporting both wild plant communities and agricultural crops.
Most ground bees are solitary creatures and, unlike honeybees, each female creates her own nest in the ground. The female will excavate her own tunnel in the soil and provision it with pollen and nectar before sealing in her eggs. The next generation is protected inside the underground chambers.
In favorable habitats, thousands of individual nests may appear in a single area, which can create dense aggregations that can persist year after year.
Nesting behavior of ground bees
Their whole life strategy revolves around soil. Species will select nesting sites based on texture, moisture, and sun exposure. Sandy or loamy soils are often preferred because of their superior drainage qualities, plus excavating these soil types is also quite easy.
Some species take this even further. They look for clay banks, compacted pathways, or sun-exposed slopes. And because of such specific nesting requirements, multiple nests often appear close together. This might give you the impression of a large colony, when in reality each burrow belongs to an individual female.
Entrance mounds mark the location of active nests. Think of these as small piles of loose soil with a hole in the center. In aggregations, the ground can look prepped with miniature volcanoes.
But despite their high visibility, ground bees are generally non-aggressive. A female is going to be far more concerned with provisioning her nest than stinging a passerby.
The most common ground bees found in the wild
Several types of ground bees are especially common in the southeastern United States, including the mining bees, digger bees, blueberry bees, sweat bees, and cellophane bees. Each has distinct characteristics:
- Mining bees: This is perhaps the most species-rich group. Adults emerge in early spring, often one of the first bee groups active each year. They are small-bodied and can form massive nesting aggregations in sunny soils.
- Digger bees: Much stockier in build, these look very much like bumblebees but lack the pollen baskets. Instead, they carry pollen on dense hairs along their legs. Digger bees will often construct turrets at nest entrances, especially in clay soils.
- Cellophane bees: This species is known for waterproofing their tunnels with a secretion that hardens like plastic. Many species fly in early spring, while others are more active in the fall.
- Southeastern Blueberry bee: The southeastern blueberry bee is a critical pollinator for commercial blueberry crops. It looks similar to digger bees but emerges earlier in the season.
- Sweat bees: This genus is highly diverse and includes many tiny species. Metallic green or dull black individuals are common in gardens and fields throughout the growing season.
Their importance to pollination
There is no overstating the ecological value of these ground bees. Each species will visit a wide range of flowering plants, both native and crops. Early spring ground nesters like cellophane and mining bees polliante maples, redbuds, apples, cherries, and blueberries. These are some plants that bloom before honeybee colonies are at full strength.
Later in the season, sweat bees and digger bees cover goldenrods, asters, and other fall wildflowers.
Specialist relationships also exist. For example, the blueberry bee is nearly undisputed when it comes to efficiently pollinating blueberry blossoms because of its buzz pollination behavior. This really makes ground bees indispensable partners in agriculture, especially for fruit growers.
How to support ground bees at home
Encourage ground bees by balancing floral resources with nesting space. Here are some easy tips for you.
- Plant early and late bloomers: Red maples, redbuds, and willows feed spring-active species. Goldenrods and asters sustain fall bees.
- Provide bare soil patches: Avoid mulching every inch of garden beds. A sunny, undisturbed patch of soil is often enough for nesting.
- Reduce chemical use: Insecticides and herbicides are poisonous for the ground bees. They disrupt both forage and soil conditions. Opt for integrated pest management whenever possible.
- Observe before acting: If soil mounds appear in your yard, watch for activity before removing them.
Closing thoughts
Ground bees are a great reminder for us all that pollination is not the work of a single species. It is more of a collective effort. A collective effort that spread across thousands of unique lineages. Their unobtrusive nests and solitary lives mask a profound contribution to ecosystems and agriculture that needs conservation.
So, the next time you stumble upon a patch of soil prepped with tiny entrances, you need to resist the urge to cover it. There are tiny pollinators working hard beneath.
For more such fun and unique insights from the world of bees, consider following my full blog here.
