Digger Bee

Digger Bee (Andrena Andrean)

Digger bee (Andrena sp.)

Digger bees in the genus Andrena are ground dwelling, solitary bees that are exceptionally good pollinators for a variety of ornamental plants and vegetable crops. There are many species of Andrena; most about ½” long and are brown to black with whitish bands of abdominal hairs. Many species fly in the spring, and the adults are generally short-lived (4 to 6 weeks). They are more active than honeybees during lower temperatures, which makes them better pollinators during the cooler spring weather. For example, they are excellent pollinators of many early blooming wild flowers and native azaleas. Digger bees are not aggressive, generally are not defensive of their nests, and rarely sting.


Digger bee (Andrena sp.)
Photo by Joseph Berger, Bugwood.org Forestry Images

When the adults emerge during April or May, they mate, and then the females will dig ¼” holes in the soil into which they place pollen and lay eggs. The young larvae remain in the nest and develop into adult bees which emerge the next spring. There is typically only one generation per year. One may find many nests in very close proximity to each other, but they are solitary insects. They may continue to use the same sites again the next year.

There is generally a small mound of soil excavated from the underground nests, and these nests are usually made in areas with sparse vegetation, such as a thin section of the lawn. It is not that the nest digging damaged the lawn, but that the lawn is usually thin where the nests are made. Nests also may be constructed near shrubs if there is not an adequate layer of mulch over the soil.

Digger bee (Andrena sp.) nest
Digger bee (Andrena sp.) nest
Photo by Whitney Cranshaw, Colorado State University, Bugwood.org Forestry Images