Nesting blocks

The MN Bee Atlas Bee Blocks project

The first phase of the MN Bee Atlas ran from 2016 - 2020, focusing on establishing baseline information about bee species living in the state. In the bee blocks part of this project, we learned about bees and wasps that make nests above ground in tunnels in dead wood or hollow plant stems. With the participation of several hundred volunteers all across the state, we mapped where different species live and what habitats they can be found in, and tracked the timing of their nesting activity. 

The bees and wasps that nest in bee blocks are solitary and gentle. Instead of forming a colony with a queen and many workers, each female makes her own small nest with a series of several cells. She provisions each cell with food (pollen for bees, insect prey for wasps) and an egg, and then seals the end of the nest with a plug of nesting material, such as mud, resin, leaves, or grass. Different species of bees and wasps plug their nests with different material, and you can often get an idea of what is nesting in the block from looking at the plugs.

Each year, volunteers hung wooden nest blocks in natural areas in the early spring and observed them twice a month for evidence of nesting activity. Blocks were returned to the Bee Atlas lab in the fall where they were overwintered and then reared the following spring so that adults could be captured and identified. Volunteer observations of nest plug completion were used to compare the seasonality of different bee species.

Check out our Species Guide to learn more about the different bees and wasps that nested in Bee Atlas blocks.

Using your own nesting blocks 

If you are interested in putting up a bee block in your yard to observe and host tunnel-nesting bees, there are many companies offering pre-made bee houses as well as directions to build your own. We like the suggestions offered by Joel Gardner, in his paper “Native Bees, Solitary Bees, and Wild Bees: What are they?” and the Xerces Society website, “Providing nest sites for pollinators”.

If you see bees using your bee house, you can submit pictures to the MN Bee Atlas iNaturalist project.