When you observe bees buzzing low over your lawn or garden and disappearing into small holes, you are likely witnessing the activity of ground-nesting bees. This behavior is common among many bee species, showcasing a fascinating aspect of their life cycle. These bees are not aggressive, and their presence indicates a healthy ecosystem.
Identifying Ground-Nestling Bees
Approximately 70% of all bee species globally are ground-nesting bees, and most are solitary. Unlike social bees like honeybees or bumblebees that live in colonies, solitary ground-nesting bees live independently. Each female constructs and provisions her own nest. While individual females are solitary, many species may nest in aggregations, with numerous nests close together in suitable soil.
Common ground-nesting bees include mining bees (family Andrenidae), sweat bees (family Halictidae), and digger bees (tribe Anthophorini). Mining bees are small to moderate, often brown or black, and hairy, emerging early in spring. Sweat bees vary greatly in appearance, often exhibiting metallic colors like green or blue. Digger bees are robust, hairy, and can be large, up to 3 cm, with visibly protruding faces.
The Purpose of Their Tunnels
Ground-nesting bees excavate tunnels in the soil to create individual nests for their offspring. These tunnels serve as protected brood chambers where each female lays her eggs. The structure involves a main burrow extending into the ground, from which several side chambers or cells branch off.
Within each cell, the female bee deposits a mixture of pollen and nectar, known as a pollen ball. This food source sustains a single larva throughout its development. After laying an egg on this supply, the female seals the cell, ensuring the larva has all the nourishment it needs to grow, pupate, and emerge as an adult bee. This method of providing all food at once is known as “mass provisioning.”
Coexisting with Ground-Nesting Bees
Ground-nesting bees are docile and rarely sting, making them safe to have around children and pets. Unlike honeybees, they do not have a large honey store or a hive to defend, which reduces their defensive aggression. A female ground-nesting bee will only sting if she feels directly threatened, such as being stepped on or roughly handled.
These bees are important pollinators, often more efficient at pollinating certain plants than honeybees. They contribute significantly to the pollination of various crops and wildflowers. Their presence also benefits soil health through aeration and nutrient cycling as they dig their burrows.
To coexist with ground-nesting bees in your yard, leave them undisturbed. Their activity is seasonal, lasting only a few weeks. Avoiding pesticides in nesting areas helps protect these beneficial insects. If their presence is a concern, altering soil conditions, like increasing turf density or tilling and adding organic matter, can discourage nesting. Professional intervention is rarely necessary, as these bees pose little threat and provide valuable ecological services.