While many associate bees with communal hives, over 70% of the approximately 20,000 bee species are solitary, nesting underground. These ground-nesting bees are common in various habitats, often preferring areas with exposed soil. Each female constructs and provisions her own nest independently.
Common Ground-Nesting Bee Species
Several common types of bees build their nests in the ground, each with distinct features. Mining bees, belonging to the genus Andrena. They are medium-sized, ranging from about 0.3 to 0.7 inches long, and are black or dull metallic blue or green with moderate hair, appearing with pale bands on their abdomens. Female mining bees have distinctive velvety patches, called foveae, between their large compound eyes and antennae bases, and long hairs on their hind legs for pollen collection.
Sweat bees, part of the Halictidae family, are another diverse group of ground nesters, often attracted to perspiration for moisture and salts. These bees are small to medium-sized, ranging from 0.12 to 0.75 inches, and can be black, brown, or brightly colored with metallic greens, blues, or even some reds and purples. While many sweat bees are solitary, some species can be social, with interconnected underground tunnels.
Digger bees, primarily from the tribe Anthophorini, are robust and hairy, often measuring up to 1.2 inches long. Many species have visibly protruding faces and their abdomens can be banded, sometimes with metallic blue. Each female digs and maintains her own nest, though they often nest in large aggregations. Males of some digger bee species may have pale white or yellow facial markings.
Characteristics of Ground Nests
Ground bee nests appear as small, distinct openings in the soil, often surrounded by a small mound of excavated dirt. These entrance holes measure between 1/4 to 1/2 inch in diameter. The appearance of the excavated soil can resemble miniature volcanoes or ant hills, though ground bee mounds are often made of grains of dirt that are not uniformly sized.
Ground-nesting bees prefer specific locations for their nests. They choose areas with exposed soil, sparse vegetation, and good drainage. Sunny, well-drained spots are favored, with some species showing a preference for sandy soils or even south-facing slopes, which dry out quickly and warm efficiently. The internal structure of these nests consists of cylindrical tunnels that lead to individual brood cells. Females provision these cells with a mixture of nectar and pollen, known as “bee bread,” for their offspring before sealing them off. These brood cells are located between 6 to 16 inches below the soil surface, though some tunnels can extend much deeper.
Coexisting with Ground Bees
Ground-nesting bees are docile creatures and pose little threat to humans or pets. Unlike social bees that defend a large communal hive, ground-nesting bees are solitary, with a single female occupying each nest. They rarely sting unless directly provoked or stepped on. Male ground bees, which are often seen hovering around nest sites seeking mates, do not possess stingers and are harmless.
These bees are important pollinators, contributing significantly to the health of ecosystems and agricultural crops. They can be more efficient pollinators for certain plants than honeybees. Their digging activity also provides a natural aeration benefit to the soil.
To coexist with ground bees, leave them undisturbed. If their presence is a concern in high-traffic areas, encourage them to relocate by keeping the soil consistently moist, as they prefer dry conditions. Reseeding bare patches or applying a thick layer of mulch can also make an area less appealing for nesting. Avoiding the use of pesticides is important for protecting these beneficial insects.