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.
Habitat: Woodland, gardens and orchards
Development: Complete metamorphosis
Food: Herbivore
Flight Period: Early-late spring, a few active in summer.
Description: small to medium sized bee, with a blue/green
metallic body which is moderately hairy.
Length: 0.5 inches
Wingspan: 1 inch
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.
The bee's basic nutritional requirements are similar to those of humans; they need proteins, carbohydrates,
minerals, fats/lipids, vitamins, and water. Learn More!
Take this quick quiz and see how much you know about Bumble Bees—our favorite essential pollinators
working around the world. This quiz is intended for fun, in a random-facts-can-be-cool kind of way.
Wild bees need our help. Many populations are declining due to habitat loss, disease and pesticide poisoning.
Each of us can create habitat to support local bee populations.