While many envision honeybees in suspended hives, this represents a small fraction of bee diversity. A significant majority, about 70% of over 20,000 known bee species, nest underground, creating complex tunnel and chamber systems.
The World of Ground-Nesting Bees
Ground-nesting bees excavate their homes directly within the soil. They create intricate networks of tunnels and individual chambers to lay their eggs and provision their young. This nesting strategy is globally prevalent, found across various continents and climates. Unlike social bees that live in large colonies, many ground-nesting bees are solitary, with each female constructing and managing her own nest.
Common Ground-Nesting Bee Species
Numerous common bee species are known for their subterranean nesting habits, each with distinct characteristics.
Mining bees (Andrena spp.) excavate burrows in soft, sandy soil, often in areas with abundant flowers. Their nests are typically marked by small, volcano-shaped mounds of soil at the entrance. While individual females maintain separate nests, many may aggregate in suitable areas.
Sweat bees (Halictus and Lasioglossum spp.) are a diverse group, with most species nesting in the ground, though some may use rotten wood. These bees can exhibit a range of social behaviors, from solitary to communal or even primitively eusocial. They often prefer well-drained, sunny patches of bare or sparsely vegetated ground.
Digger bees (Anthophora spp.) are common ground nesters, often mistaken for bumblebees due to their furry, stout bodies. They establish their nests in well-drained soils, including clay, and can sometimes be found burrowing into banks or between stones. Their nests may feature a chimney-like turret structure at the entrance.
Why Bees Choose Underground Living
Underground living offers several ecological advantages. The soil provides a stable environment, protecting developing young from extreme temperature fluctuations and maintaining consistent humidity levels. This subterranean refuge also offers defense against predators and harsh weather conditions.
Ground-nesting bees prefer specific soil types. Many species favor well-drained, sandy, or silty soils with low organic matter. However, some, like certain digger bees, can utilize clay-rich soils.
The structure of these nests typically involves a main vertical tunnel that branches into smaller side tunnels, each ending in a brood cell where an egg is laid and provisioned with pollen and nectar for the developing larva.
Distinguishing Ground Nests from Other Bee Habitats
While many bees nest underground, it is important to differentiate this behavior from other common bee habitats.
Honeybees are highly social insects that construct elaborate wax comb hives, typically in enclosed cavities such as hollow trees, rock crevices, or human-made structures. They do not excavate extensive tunnel systems in the ground, though they may occasionally occupy abandoned rodent burrows.
Bumblebees, while sometimes found in existing cavities on or just under the ground, generally do not excavate their own elaborate tunnel systems. They are social bees that often utilize abandoned rodent burrows, dense grass clumps, or other pre-existing sheltered spaces. Their nests are insulated with materials like grass, plant stems, and fur, and are much less complex than honeybee hives.
Carpenter bees, in contrast, bore into wood to create their nests. They excavate perfectly circular holes in soft, unfinished wood, such as decks, fascia boards, or dead trees, to lay their eggs. Unlike ground-nesting bees, carpenter bees do not consume the wood but chew through it to create their galleries.