More than seventy percent of the world’s bee species make their homes underground, unlike honeybees in communal hives. These ground-nesting bees are a common presence in many environments. They are diverse insects that play a role in ecosystems.
Identifying Ground-Nesting Bees
Several common types of ground-nesting bees include mining bees, sweat bees, and digger bees. Most are solitary, with each female constructing and provisioning her own nest to raise young. Unlike social bees, they do not form colonies with a queen and worker hierarchy.
The appearance of ground-nesting bees varies across species, ranging from 3 to 16 millimeters in length. Their coloration can include shades of black, brown, metallic green, blue, purple, or even copper. Some species, like certain mining bees, may be hairy, while others, such as some sweat bees, can display metallic sheens or striped abdomens. Observing their flight pattern can also offer a clue, as many ground-nesting bees tend to fly low to the ground.
It is important to differentiate them from wasps, particularly yellow jackets, often mistaken for ground bees. Yellow jackets are typically more aggressive, emerging from a single, shared nest entrance in large numbers, unlike solitary ground bees which use individual tunnels.
Their Underground Lives
Ground-nesting bees excavate their nests underground for protection. The soil provides a stable environment, shielding their offspring from predators and offering insulation against fluctuating temperatures. This subterranean shelter also protects against elements such as heavy rainfall and wind.
Female ground-nesting bees construct their nests by digging tunnels using their mandibles and legs. These nests typically consist of a main tunnel that branches into several side tunnels, each ending in an individual brood cell. Some species line these cells with a waterproofing substance, which helps protect the developing larvae. Within each cell, the female deposits a ball of pollen and nectar, lays a single egg, and seals the cell.
The depth of these nests can range from a few inches to several feet. These bees often select warm, sunny areas for nesting, favoring well-drained, sandy soils. Their nest entrances may be marked by small mounds of excavated dirt, like miniature anthills. Many species exhibit nest site fidelity, returning to the same location year after year.
Interaction and Importance
Ground-nesting bees are non-aggressive and pose a minimal stinging risk. Unlike social bees that defend a communal hive, solitary ground bees lack a large colony to protect, making them less inclined to sting unless directly handled, stepped on, or provoked. The males of these species do not possess stingers at all.
These bees play a role as pollinators in ecosystems. Many species emerge early in the spring, making them pollinators for early-blooming plants, including fruit trees such as apples, cherries, and blueberries. Some ground-nesting bees are specialist pollinators, focusing on specific plant species, making them efficient. Beyond their pollination services, their tunneling activities can also provide soil aeration.