Mason Bees

The orchard mason bee (Osmia lignaria) is a gentle beneficial insect that pollinates fruit trees and other early blooming flowers. It is found throughout most of North America. The orchard mason bee is usually slightly smaller than a honey bee and a shiny dark blue in color.

The female uses existing holes in wood for a nest, especially in dead or decaying trees. She chooses holes slightly larger than her body, usually 1/4 to 3/8 inches in diameter. The bee first places a mud plug at the bottom of the hole, then brings in 15 to 20 loads of nectar and pollen which she collects from spring flowers, including apples and other fruits. When the female has provided a sufficient supply of food for the larva, she lays an egg and then seals the cell with a thin mud plug. She then provisions another cell, and continues in this fashion until the hole is nearly full. Finally the bee plasters a thick mud plug at the entrance.

The female orchard mason bee lives for about a month and can produce one or two eggs each day. The larva hatches from the egg after a few days and begins to eat its provisions. When the pollen-nectar mass is completely eaten in about 10 days, the larva spins a cocoon and pupates within the cell.

Near the end of the summer the bee transforms to the adult stage but remains in the cocoon throughout the winter. In the spring, when the weather has warmed up sufficiently, the bees chew their way out of the cocoon.

Mason bee straws:

The straws we use at House of Bees have an outer “guard” tube as well as an inner paper liner. Before putting the mason bee house outdoors, fold over the excess paper, and insert that end first. This closes the back of the straw and leaves an end that you’ll be able to use to easily remove the paper liner from the guard tube when processing the cocoons. Parchment paper can be rolled around a pencil or dowel and inserted into the guard tube, in place of the paper liner.

Mason bee houses:

Position the mason bee house where it will receive morning sunlight and is protected from weather, such as the south or eastern side of your home or other structure. You may also place the mason bee house on a dead tree or post in wooded areas near streams where there is a good supply of mud for nest construction.

Mason bee calendar:

February/March: Establish a location and install the bee house in an area where you’ll be able to observe them. The female bee will begin to fill the straws with eggs, pollen and mud.

Mid-June: Remove filled straws (leaving guard tube and liner intact) and store in a warm, dry, sheltered location away from hot sun. This could be a shed, garage, or attic. It is important to move the straws to protect them from predatory wasps and woodpeckers. Handle the straws gently, and keep them level.

September/October: Bees are now fully developed in their cocoons. Move the straws to a cool location, such as an unheated out-building, for winter hibernation.

October through December: Open the straws to clean the cocoons and discard debris and mites. Do this in a cool, dry location. There are excellent videos on YouTube that show step-by-step details for this process.

February/March: Place the bee house and cocoons outdoors in a sheltered location to start the process over again, to build a healthy mason bee population.