The common image of a bee involves a honeybee hive hanging from a tree or in a wooden box, but this represents only a small fraction of the world’s bee species. A vast majority of bees, over 70%, are ground-nesters, making the soil the most common location for a bee home. These species, which include many of the world’s approximately 20,000 bee species, are typically solitary and build their nests beneath the surface. Understanding how and where these bees build their nests is the first step toward appreciating their role in the ecosystem and coexisting with them.
Which Bees Nest in the Earth
Bees that nest in the soil fall into two major categories based on their lifestyle: solitary species and social species. Solitary bees, such as Mining Bees (Andrena species) and Sweat Bees (Halictidae family), make up the bulk of ground-nesters. Each female constructs and provisions her own nest independently, acting as her own queen. She stocks the nest with a mixture of pollen and nectar, known as “bee bread,” lays a single egg on it, and then seals the cell.
A much smaller number of ground-nesters are social, most notably certain species of Bumblebees (Bombus genus). A bumblebee queen establishes a colony with worker bees that help raise subsequent generations. Bumblebee colonies are annual, lasting for only one season, and they often utilize pre-existing cavities for their nests. This difference in life cycles—a solitary female working alone versus a large, cooperative colony—dictates their respective nesting architectures.
The Architecture of a Ground Nest
The physical structure of a ground nest varies significantly between solitary and social bees. Solitary ground-nesting bees excavate a single main tunnel that descends into the soil, typically a few inches deep, though some go as deep as 10 feet. Off this main tunnel, the female digs several lateral tunnels, each ending in a separate, sealed brood cell. Each cell is provisioned with the pollen and nectar mixture and then sealed, creating a secure chamber for the developing larva.
A social ground nest, such as that of a bumblebee, is generally less structured and relies on an existing underground cavity. The queen often selects an abandoned rodent burrow or a dense clump of grass, utilizing insulating material left behind by the previous occupant. Inside this larger cavity, the bumblebees construct wax pots for storing nectar and pollen and build brood cells that appear less organized than a honeybee’s hexagonal comb. The architecture of both solitary and social nests helps with temperature regulation and moisture control, protecting the developing brood.
Identifying and Coexisting with Ground Bees
Identifying a ground nest is usually straightforward, as both solitary and social nesters leave distinct signs at the soil surface. Solitary ground bees, such as Mining Bees, create small, volcano-shaped mounds of excavated soil with a clean hole in the center, typically about a quarter-inch in diameter. Although each female has her own nest, they often nest in “aggregations” where dozens or hundreds of individual nests cluster in one area of bare, well-drained soil. Bumblebee ground nests are marked by a single entrance hole that bees fly in and out of constantly, often beneath a tuft of grass or a rock.
The presence of ground bees is rarely a cause for concern because solitary species are non-aggressive and lack a colony to defend. Females only sting if they are physically handled or accidentally stepped on. Males, often seen flying low over the ground, do not have stingers at all. To coexist with these beneficial pollinators, which also help aerate the soil, simply avoid disturbing the nesting area during their active period in the spring. If you find an aggregation, allow them to complete their short, four-to-six-week nesting cycle undisturbed.