The world of bees encompasses over 20,000 known species, and their living arrangements are far more diverse than the familiar image of a single wooden box. Found on every continent except Antarctica, these insects have evolved specialized nesting strategies to survive across every habitat containing flowering plants. Understanding these varied habitats reveals the complexity of these globally important pollinators.
Large Social Colonies Above Ground
The most recognizable bee dwelling is the large, perennial colony of the honeybee. Wild colonies select large, dark, protected cavities, such as hollow tree trunks, rock crevices, or voids in human-made structures. Scout bees search for a space that is dry, well-insulated, and typically offers a volume of about 40 liters with a small, defensible entrance.
Within this sheltered space, worker bees secrete wax from glands on their abdomens to construct the intricate, hexagonal comb. These cells, measuring approximately 5.5 millimeters wide, are used for both raising new bees and storing food reserves like honey and pollen. The architecture features a central sphere of brood comb, which is insulated and temperature-regulated by the colony, surrounded by outer layers of stored nectar and pollen.
Bumblebees (Bombus) also form social colonies, though their structure is different, operating on an annual cycle. A single queen emerges in spring to found a new nest, which typically grows to contain only 50 to 400 individuals before dying off in the autumn. These queens are opportunistic, seeking out existing cavities rather than constructing a hive from scratch.
Common nesting sites for bumblebees include abandoned rodent burrows, dense tussocks of grass, compost piles, or gaps beneath sheds. The queen lines the chosen cavity with soft, insulating materials like moss, dried grass, or animal fur. Inside, the queen constructs small, irregular wax pots for nectar storage and less-organized wax brood cells, contrasting sharply with the precise, multi-layered comb of the honeybee.
Solitary and Semi-Social Ground Nests
The majority of bee species, roughly 70%, live solitary lives and choose to nest in the earth, such as Mining Bees (Andrena) and Sweat Bees (Halictidae). Each female operates independently, excavating and provisioning her own nest without the help of a worker caste. The selection of a nesting site is highly specific, favoring patches of bare, uncompacted soil that are exposed to sunlight, often on south-facing slopes.
These bees prefer well-drained soil types, including sandy-loam, silt-loam, or certain kinds of clay, which offer stability for tunneling while allowing for easier excavation. The female digs a primary vertical shaft, or main burrow, which can descend between 6 and 16 inches. From this main shaft, she excavates short, lateral tunnels, each culminating in a single brood cell.
In a process known as mass provisioning, the female gathers a large, single supply of pollen mixed with nectar and places it inside the cell. A single egg is then laid directly on top of this provision mass, and the cell is sealed. Some species line the cell walls with a waxy, waterproof secretion from a specialized gland, protecting the developing larva from soil moisture before the lateral tunnel is backfilled with earth.
While these bees are solitary, they frequently nest in dense aggregations, where hundreds or even thousands of nest entrances may be clustered together. This creates the appearance of a colony, marked by small, volcano-like mounds of excavated soil. However, the females remain solitary, with each bee responsible for the entire construction and provisioning of her own offspring.
Cavity and Tunnel Dwellers
Mason Bees (Osmia) and Leafcutter Bees (Megachile) are cavity and tunnel dwellers, utilizing existing voids. Unlike ground-nesting species, these bees do not excavate their own tunnels but instead seek out existing cylindrical spaces. Such sites include hollow plant stems, abandoned beetle borings in dead wood, or pre-existing gaps in masonry.
The female divides the linear tunnel space into brood cells, starting at the deepest point. Mason bees are named for their habit of gathering wet mud or clay, which they use to construct the partitions separating each cell. After provisioning a cell with a pollen and nectar ball and laying an egg, the female constructs a thick mud wall before starting the next cell.
Leafcutter bees employ a distinct method, using their mandibles to precisely cut semi-circular pieces from soft leaves or flower petals. They meticulously manipulate these pieces to form thimble-like cells, which are then provisioned and sealed. For both groups, the female typically lays the fertilized eggs, which will become females, in the protected back of the tunnel, reserving the unfertilized male eggs for the cells closer to the entrance.