Mason Bee, Osmia spp.

Mason bees are common in the United States, especially in forested regions, but they are also found in many other parts of the northern hemisphere. About 140 species of mason bees are found in North America out of about 200 species worldwide. Mason bees are named for their habit of using mud or other "masonry" products in constructing their nests, which are made in naturally occurring gaps such as between cracks in stones or other small dark cavities

Mason bees are generally smaller than honey bees, but some are about the same size as honey bees or slightly larger. They have stout bodies, and many species are metallic green or bluish in color. Unlike honey bees, Mason bees are solitary.

Mason bees emerge from their cocoons in the spring. Males emerge first and remain near the female nest and try to extract females from their cocoons. When the females emerge, they mate with one or more males. Males soon die and females begin to provision new nests.

The females soon begin to collect pollen and lay eggs. Larval bees feed for several weeks inside their closed cells. They pupate in late summer and spend the autumn and winter as adults inside their pupal cocoons in the nest. They emerge from the cocoons in the spring, coinciding with flowering of many orchard crops. The new generation of bees then begins the cycle over again.

Mason bees are very effective pollinators. Two or three females can pollinate the equivalent of a mature apple tree in one season. Their range of plant pollination is several hundred feet so they are useful for gardens and small orchards. They fly in cool or rainy weather and can supplement or replace honey bees as commercial pollinators in some situations.

Help Homeless Mason Bees

Since Mason bees do not use hives like honeybees. In nature, mason bees place their eggs in holes drilled by beetles or woodpeckers. The bees will also use spaces between roof shingles or other narrow openings around the garden. There are a number of commercial products that you can purchase to house mason bees or you can make your own!.

Once you have your mason bee house, the first step will be deciding where to hang it. The optimal location to hang your mason bee house is 6 to 7 feet off the ground, preferably under an eave of your house, garage, shed or some other shelter. If this is not an option, choose a house design that provides adequate shelter from the elements on its own

After bees mate, the female places eggs in the holes. Each egg is separated by nectar and pollen—it is at this time that the bees’ pollen-gathering also pollinates plants.

After the pollen and nectar is placed, the female places a mud plug in the tube (hence the term “mason”), then repeats the process with more eggs, pollen, nectar and plugs. When the tube is full, she finishes with a heavy mud plug and her work is done.

In the spring, the mature bees emerge from theholes. Males exit first. Females emerge after males because the eggs are placed deeper in the tubes. This is a protective measure, assuring a good female population to help keep the species going.

Further Information:   

☆ Wisconsin Bee Identification Guide
☆ Spring Wild Bees of Wisconsin
☆ Bumble Bees of Wisconsin
☆ Wild Native Bee Nest Boxes

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Spring Pollinator Plants

Spring begins andhungry pollinators are on the wing, looking for food. From the moment emerge in spring to the time that they hibernate or migrate in the fall, pollinators need to eat.

• Bumble Bees
• Carpenter Bees
• Dark Striped Bees
• Green Sweat Bees
• Honey Bees
• Leafcutter Bees
• Mason Bees
• Mining Bees
• Small Sweat Bees