Digger bees are a large, diverse group of native insects often noticed in early spring when they create small mounds of soil in yards and gardens. These insects are solitary bees, meaning they do not live in a communal hive with a queen or worker caste like honeybees or yellow jackets. The small, volcano-shaped holes they leave in the ground are the reason people become aware of their presence. These ground-nesting insects are generally harmless and play an important role in the local ecosystem.
Defining Digger Bees and Their Appearance
The common name “digger bee” is applied to numerous species of ground-nesting bees belonging to several families, most notably those in the genus Anthophora. These insects are distinguished by their robust and often hairy appearance, which helps them effectively gather pollen. They typically measure between one-quarter and three-quarters of an inch long, placing them in the medium-sized range for native bees.
Physical coloration varies widely by species, presenting as dark brown or black, sometimes with pale abdominal banding, or possessing metallic sheens or markings in yellow, white, or rust. Female digger bees have dense hair on their bodies and legs specialized for carrying pollen back to their underground nests. Unlike social wasps, digger bees have a fuzzier, more compact look that can sometimes cause them to be mistaken for small bumble bees.
Solitary Nesting Behavior
Digger bees are named for their solitary, subterranean nesting habit. Each female digs a cylindrical tunnel into the earth to create a home for her offspring. These burrows are typically established in areas with dry, well-drained soil that has sparse vegetation or bare patches, often reaching a depth of about six inches.
The female bee constructs multiple individual chambers, or cells, off the main tunnel, which are waterproofed with a secreted substance. She provisions each cell with a mixture of nectar and pollen, often called “bee bread,” which serves as the sole food source for a single larva. Once provisioned, an egg is laid, and the cell is sealed, allowing the larva to develop and pupate underground until it emerges as an adult the following spring.
Although solitary, multiple females often nest in the same suitable patch of soil, creating a dense grouping of individual tunnels known as an aggregation. This clustering can give the false impression of a large colony, but there is no shared defense or social structure. The mounds of soil visible on the surface are simply the excavation byproduct from the female’s digging.
Ecological Role and Safety
Digger bees are valued native pollinators because they are among the earliest bees to emerge in the spring. Their activity is timed to pollinate many native wildflowers and early blooming fruit trees and crops before other bee species become fully active. This early-season foraging makes them a significant component of the local plant reproduction cycle.
Digger bees are non-aggressive and pose very little threat to people or pets. They do not have a communal hive or colony to defend, eliminating the defensive swarming behavior seen in social insects like yellow jackets or honeybees. The males lack a stinger entirely, and females will only sting if they are handled, stepped on, or severely provoked. If their presence is undesirable, the most effective approach is non-lethal habitat modification, such as thickening the turf or watering the area to make the soil less appealing for nest construction.