Not all bees reside in familiar hives; many species create intricate nests beneath the earth’s surface. These ground-nesting bees are widespread across various ecosystems and fulfill significant roles in the natural world. They often lead solitary lives and are generally non-aggressive. Their presence highlights the diverse nesting strategies within the bee community and their valuable contributions to healthy environments.
Common Ground-Nesting Bee Species
Several types of bees construct nests in the ground, each with distinct characteristics. Mining bees (Andrena) are frequently encountered ground nesters, appearing in early spring. These bees typically create small, volcano-shaped dirt mounds, often in well-drained soil, and are important pollinators of fruit trees and other spring plants. Digger bees (Anthophora) are larger and often fuzzy, sometimes resembling bumblebees. They are known for building distinctive turrets or chimneys at their nest entrances and prefer sandy or clay soils.
Sweat bees (family Halictidae) encompass diverse species, ranging from black to bright metallic green. While many sweat bee species are solitary, some can be social, with interconnected tunnels underground. These bees are attracted to perspiration, hence their common name, and are efficient pollinators. Cellophane bees (Colletes) waterproof their underground nests with a unique, cellophane-like substance. They often form large aggregations of individual nests, particularly in early spring, and prefer sandy soils on south-facing slopes.
Characteristics of Ground Nests
Ground bee nests are identifiable by small, distinct structures on the soil surface. These nests usually appear as miniature volcano-shaped mounds of excavated soil with a central entrance hole, often about 1/4 to 1/2 inch in diameter. While each nest is generally the work of a single female bee, multiple solitary nests may be found in close proximity. These bees prefer to establish nests in sunny, well-drained areas, particularly in patches of bare ground or where vegetation is sparse.
The internal structure of a ground bee nest involves a main tunnel that extends downwards into the soil, often reaching depths of a few inches to nearly 10 feet, depending on the species. From this main tunnel, female bees excavate side tunnels, each leading to individual brood cells. Within these cells, the female deposits pollen and nectar for her offspring before laying a single egg and sealing the chamber. This provides a stable and protected environment for the developing young.
Behavior and Ecological Significance
Ground-nesting bees are primarily solitary insects; each female constructs and provisions her own nest. This solitary nature means they lack a large hive to defend, making them generally non-aggressive and unlikely to sting unless provoked. The bees seen flying actively near nest entrances are often males, which lack stingers and are primarily searching for mates. Their docile temperament distinguishes them from social insects like honeybees or yellowjackets, which defend communal nests more vigorously.
Beyond their calm demeanor, ground bees play a significant role in ecosystem health as pollinators. They are highly efficient at transferring pollen and nectar, often contributing more effectively to the pollination of certain plants than honeybees. Many species are among the first pollinators to emerge in spring, making them important for early-blooming crops and wildflowers. Their burrowing activities also contribute to soil aeration, improving water penetration and nutrient cycling in the ground.
Coexisting with Ground Bees
Encountering ground-nesting bees is common, and peaceful coexistence is often the most suitable approach. Since these bees are generally non-aggressive and temporary residents, leaving them undisturbed is usually the best option if their nests are not in high-traffic areas. Their nesting season typically lasts only a few weeks in the spring, after which the bees complete their life cycle, and the nests naturally disappear.
To minimize accidental encounters, wearing shoes in areas with nests can provide protection. Observing the bees from a distance also allows for appreciation of their natural behavior without disturbance. If discouraging nesting in a specific area is desired, non-harmful methods can be applied after the nesting season. Increasing irrigation in the affected soil, applying mulch, or planting dense ground cover can make the area less appealing for future nesting, as ground bees prefer dry, sparsely vegetated soil. If concerns persist or identification is uncertain, contact a local university extension office or a pest control service specializing in humane insect management.