When small mounds of soil appear in a lawn or flower bed, often accompanied by insects flying low to the ground, people frequently assume they are dealing with aggressive ants or social wasps. This common sight is most often the activity of native ground-nesting bees, which represent the majority of the world’s bee species. An estimated 70% of all bee species utilize the earth for shelter, laying their eggs in subterranean burrows rather than in centralized hives. These insects are overwhelmingly solitary, meaning each female constructs, provisions, and protects her own nest without the labor division of a colony structure. Understanding their identity and behavior is key to appreciating their significant ecological role.
Identifying the Common Ground Nesters
The vast majority of ground-nesting bees belong to a few common families, all categorized as solitary bees. One of the most frequently encountered groups in temperate regions is the Mining Bee (Andrena). These bees are often small, dark, and covered in pale yellow or reddish hair on their thoraxes. They are among the earliest bees to emerge in the spring, often becoming active when the first trees and wildflowers begin to bloom.
Another widespread group is the Sweat Bee (Halictidae), which are highly diverse. They are recognized by their small size and sometimes striking metallic coloration, exhibiting shades of iridescent green, blue, or copper. Some sweat bee species display a primitive form of sociality, while many others remain strictly solitary. Their small burrows often aggregate in high-traffic, sunny areas.
Digger Bees (Anthophora) and Cellophane Bees (Colletidae) are also common ground nesters. Cellophane bees, sometimes called plasterer bees, line their brood cells with a polyester-like secretion that acts as a waterproof barrier. Although many solitary nests can be found close together in a favorable patch of soil, each small hole represents the independent work of a single female.
Solitary Life Cycle and Nest Structure
Female ground bees seek specific environmental conditions to establish their nests, typically preferring well-drained, sandy, or lightly compacted soil exposed to the sun with sparse vegetation. Once a suitable spot is located, the female excavates a vertical or slightly angled main tunnel, which can extend over six inches deep. She then digs several short, horizontal side tunnels that terminate in small, oval-shaped chambers known as brood cells.
The female provisions each cell with a specialized food source for her offspring. This mixture, known as “bee bread,” is a nutrient-rich paste made from collected pollen mixed with nectar, enzymes, and the female’s saliva. The addition of these digestive enzymes begins a fermentation process. She then lays a single egg on top of the bee bread within the cell before sealing the chamber shut.
Once the female has provisioned all her cells, she completes her life cycle and dies, leaving the next generation to develop underground. The larva hatches and consumes the bee bread over several weeks, developing into a prepupa that overwinters deep within the sealed cell. After spending up to 11 months underground, the adult bee emerges the following spring to mate and begin the cycle anew.
Temperament and Coexistence
The sight of numerous bees flying low to the ground often triggers fear, but solitary ground bees are non-aggressive and pose minimal threat to humans or pets. Unlike honeybees or social wasps, solitary species have no communal hive or honey stores to defend. A female ground bee’s only concern is her individual, provisioned brood cells, and she has no instinct to sacrifice herself to protect an entire colony.
A female will only sting if she is accidentally trapped, squeezed, or stepped on. Males, which are often the most numerous individuals hovering in mating displays near the nest openings, do not possess a stinger at all. This gentle behavior differs significantly from social wasps, which are known for their territorial defense and willingness to sting repeatedly when their single-entrance colony is disturbed.
Because their active season is generally short, lasting only a few weeks in the spring, eradication is rarely necessary or recommended. Homeowners can promote coexistence by avoiding walking barefoot over the aggregation area and by postponing major lawn work until the bees’ brief period of activity has ended. Ground-nesting bees often return to the same location year after year because the soil conditions are ideal, making it beneficial to leave the area undisturbed.
Importance in Local Ecosystems
The presence of ground-nesting bees is a positive indicator of a healthy local environment, as they provide essential pollination services to native flora. Many of these species are described as oligolectic specialists, meaning they collect pollen from only a narrow range of plant species. This specialization makes them efficient pollinators for those specific plants.
For instance, the Spring Beauty bee is a specialist that targets the Claytonia flower. This specialized relationship often makes native ground bees more effective at pollinating certain crops and wildflowers than generalist species like the honeybee. The efficiency of these native pollinators means that even a small population contributes significantly to the health and biodiversity of a landscape. Supporting these bees, which are sensitive to environmental changes, helps maintain the resiliency of local plant communities.