I have been seeing a lot of mining bee nests recently (Andrena sp.). It seems the hot early spring weather has set them into a nest building frenzy! These beautiful little bees build themselves curious structures that look like miniature volcanoes. They are usually around 5cm high, made of bits of soil, usually with a hole around 4mm wide at the top.
The little mound is the entrance to the nest, which is built by the female. It can go up to 60cm down, and contain many chambers for her eggs. Sometimes there may be several in the same patch of lawn, but they won’t be connected and aren’t part of a communal nest.
Mining bees can be found in loose groups, but are not social insects like honey bees or paper wasps. They are ‘sub-social’. This means that they don’t have a hive and divide labour between workers and queens like fully social bees and wasps. They have a commune-like system where there all live in the same place. They are closely related and share resources including food locations, but they rear their own young. They are primitive social insects.
The mining bee is harmless
In the garden Mining bees are extremely beneficial insects. They pollinate many different types of plants and their burrowing does not harm plants. It can also be beneficial in aerating the soil. If they are really causing a problem, wait until autumn/winter and turn the soil over in that area. The nesting chambers won’t be that deep and it should prevent recurrence the following year.
These solitary bees are valuable additions to your garden. They are harmless and do not sting. My advice is to just let them go about their business.