Mason bee is a common name for species of bees in the genus Osmia, of the family Megachilidae.

Masons vs. Honeybees

Our native Mason bees have lived in America for millions of years. We call them

Masons because they work with mud to build and seal their nests. Honeybees were

introduced by Europeans just 400 years ago—and we all love their honey. But lately,

honeybee numbers are much reduced through parasitic mites and mystery diseases that

are wiping out their hives.

Mason bees are excellent spring season pollinators and, since they have no honey to defend, will only sting if squeezed or stepped on. As such, they make excellent garden "pets", since they both pollinate the plants and are safe for children and pets.

Osmia species are usually metallic green or blue, though many are blackish and are smaller than other bees.

Homeowners sometimes become concerned when they see the bee entering cavities under shake siding or investigating nail holes or other cavities in wood during March through early June. These are not destructive insects, since they do not excavate holes in the wood, though they will clean out loose debris. No controls are recommended, since no damage is done. To prevent the bee from nesting, holes may be filled with caulking.

Attracting Mason Bees
In the wild, Masons build their
mud sealed nests in natural tubes like
reeds or holes in dead trees. Sometimes
they’ll make homes between
wood shingles on houses and barns.
(They do no damage—they just build
their mud homes in sheltered cracks.)
Now extensive research by the US
Department of Agriculture has proved
that the Mason bees’ task is made
much easier if we provide 6" paperlined
tubes 5⁄16" in diameter, that are
somewhat weatherproof and contained
in a protective shelter. The smooth
tubes we humans can supply mean the
female Mason has a lot less prep work to do
on her nest—and she can channel that extra
time and energy into laying more eggs.
Position Nest Kits firm and level in a
sheltered sunny spot, facing East or South,
where it won’t be disturbed. 6 to 8 ft. high
is a good height.
Other Native Bees
Besides the Orchard Mason Bee (Osmia
lignaria) you may attract a couple of leaf
cutter bees as well, depending on where you
live. Osmia montana uses chewed leaves
as a building material—so it looks green.
Osmia californica uses a blend of leaves
and dirt. They’re helpful pollinators too.

The Mason Bee life cycle
Those mud sealed tubes contain the whole
future population of Masons, males and
females. All of last year’s adults have
completed their lives by the end of the
previous Spring. Each 6" tube contains
6 or 7 separate compartments, each with
one egg and a food store pellet of pollen
and nectar. In summer, the eggs hatch and
the grubs feed. By September, they are
transformed into adult bees that stay in
their snug mud home until blossom time
the following Spring.
Cleverly, the Mason Bee mothers have
laid female eggs in the 4 or 5 most protected
inner compartments—and just a
couple of male eggs near the outside. The
males chew their way out first into the
warm Spring sunshine and eagerly await
the coming out of the female debutantes.
Mating is over quickly and the females
devote the rest of their short, busy lives to
finding a nest site, locating mud, making
one cell at a time, provisioning it, laying
one egg, sealing with mud—and on to
the next one.
Because they are so docile, you can
stand close to the tube and see the
females going in frontwards with either
mud or food pellets—then backwards in
order to lay their eggs. Sometimes, they’ll
just sit on the front porch of their tube
and visit in neighborly fashion. Though
each female is in complete charge of her
own house and nesting arrangements,
they’re quite gregarious and seem to like
living in groups.

Starter nestiing kits with 20 tubes and holder - $14.99

Large nesting kit with 104 tubes and holder-$29.99