By Amber Barnes and Laura Jach Smith
Female (left) and male (right) mining bees on golden Alexander leaf and flower—photo credit: Amber Barnes
Here is a pollinator you have probably been seeing all spring: bees from the genus Andrena, known as mining bees. These solitary bees build their nests in sandy soils by mining tunnels underground where they lay their eggs and tend to their young. Their nests are often found nearby the wildflowers that they are pollinating. Early spring is a time of year when you might find a mining bee’s tunnel, before vegetation has grown thick, and exposed areas of soil are still noticeable. Mining bees usually select bare patches of ground to dig their tunnels, and often live near one another. This makes it appear that there is a colony, but it’s more like an apartment complex. They tolerate close neighbors but keep to their solitary nature, each having their own nest.
Entrances to mining bee nests can be seen with soil piled up next to a small tunnel—photo credit: Amber Barnes
These ground-nesting bees are docile, non-aggressive bees. A female would have to be stepped on before they would sting, and even then her stinger is so small, it’s unlikely to penetrate the skin. Aside from early spring ephemerals, mining bees are excellent pollinators for many of our early-blooming fruit trees such as apple, cherry, and plum; blueberries; and other flowering trees and shrubs. Allowing bare patches of ground that provide nesting habitat for mining bees is a simple step many landowners can take to support important native bees who provide pollination services that help secure our food supply. Once she’s excavated a nest, female mining bees then make balls of pollen and nectar for each egg in the brood cell chambers (see illustration). Minimal disturbance of the site is required, as the new adult bees do not emerge until the following spring, so one can imagine that practices such as tillage would destroy any mining bee nests.
A mining bee’s tunnel system—Illustration by Steve Buchanan
Some mining bees are very particular with their pollen and nectar source. Oligolectic bees refer to bees who are specialist pollinators and only rely on a single type of flowering plant. There are many Andrena spp. that specialize in pollinating one type of plant (see Illinois Wildflowers “Oligolectic Bees,” https://www.illinoiswildflowers.info/flower_insects/files/oligoleges.htm). If you visit a woodland with a nice patch of spring beauty (Claytonia virginica) in bloom, you will likely see the flowers abuzz with their specialist pollinators, the spring beauty miners (Andrena erigenidae) that rely exclusively on spring beauty pollen to feed their brood. They fill their scopa (the pollen-collecting hairs on their rear legs and thorax) with the pink pollen of spring beauties before flying back to their nest.
Spring beauty mining bee—photo credit: Laura Jach Smith
Want to know what kind of bees you might be seeing in your yard this year? Here is a great quick-start guide to help you differentiate between some of the different types, such as honey bees, bumble bees, leaf cutting-bees, mining bees, sweat bees, carpenter bees, etc.: https://www.pollinator.org/bee-id-blog
For any questions or conversation, please feel free to reach out to [email protected] and a representative from P2 will get back to you! Thank you for your interest in pollinator conservation!
Amber Barnes and Laura Jach Smith are biologists with Pollinator Partnership (P2). Over the years, Amber has led several of P2’s Monarch Wings Across America efforts, including Project Wingspan and Monarch Wings Across Ohio. As Conservation Program Manager, she is now working with P2 staff throughout the country to provide pollinator-related education, outreach, and support to agricultural landowners and producers. Laura is P2’s former Project Wingspan State Coordinator and current Wisconsin NRCS Pollinator Liaison. She uses her background in agro- and ecosystem ecology to advance the conservation and ecological enhancement of our natural and agricultural resources by providing pollinator-related support to the Natural Resources Conservation Service (NRCS) of Wisconsin and the producers that they serve.
