The orchard mason bee (Osmia lignaria) is a gentle beneficial insect that is a pollinator of apples, cherries, and other tree fruits and garden plants. It is found throughout most of North America, particularly in wooded areas but often around homes even in the city.
People are 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, They do not create the hole. To prevent the bees from nesting in the house, holes may be filled with caulking.
In nature they nest within hollow stems, woodpecker drillings and insect holes found in trees or wood. Sometimes there may be dense collections of individual nest holes, but these bees do not connect to each other or share nests. They do not help protect each others’ young. Also, they are active for only a short period of the year. They are not aggressive so you can get close without fear of being stung, which makes them excellent for enhancing our yards and gardens. They add beauty, activity and pollination to our plants and fruit trees. However, they do not produce honey. We are looking at all of the beneficial garden bugs for our organic garden, and Mason bees are a great addition.
About The Mason Bee
The female Mason Bee visits flowers to collect pollen for its young. She forms a small ball of pollen and nectar in the back of the nesting tube and lays an egg on the ball. She then collects mud to form a cell partition and repeats the pollen ball-egg laying process until she reaches the mouth of the tube where she caps the end with mud. Starting the life cycle in the spring, adult males emerge from tubes first, but must wait for the later appearance of the females in order to mate. This event often coincides with the redbud (Cercis) bloom. Females alone, begin founding new nests in holes to make a row of 5-10 cells in each nest. Females collect the pollen and nectar and lay eggs. Their short foraging range is about 100 yards from the nest. Activity continues 4-6 weeks and then adults die. During the summer, larvae develop inside the nests, make cocoons, and become new adults resting in the cells. With the onset of fall, the adults become dormant as they go into hibernation. These bees require some cold temperatures before spring in order to break their dormancy. The orchard mason bee is usually slightly smaller than a honey bee and a shiny dark blue in color. The actual size of the bee depends largely upon the size of the hole in which it grew.
Nest Block Construction
The native eastern species of Orchard Mason Bee will nest in holes drilled in a wooden block. Untreated 4″ x 6″ lumber works great. Holes can be drilled in the wood on 3/4 inch centers. They should be 4-8″ deep (depending upon the size lumber used), smooth, and a 5/16″ diameter hole is important. A smaller hole encourages higher production of male bees which reduces the reproductive potential of the population. Blocks may be drilled from either face giving shallower or deeper holes. Shallower holes may produce more male bees. Do not drill completely through the lumber. Drill the hole to a depth about 1/2 inch from the back of the block. Attach a roof to provide protection from the midday sun and rain. Outside surfaces may be painted or stained, but do not use wood preservatives. One hole may be drilled in the back to provide a means of hanging the block. Face nesting blocks as close to the southeast direction as possible to catch morning sun and affix it firmly so that it does not sway in the wind. It should be located at least three feet above the ground.
These bees need mud to construct cell partitions, so adding a mud supply may be helpful if needed. This can be a trench or tub located nearby where muddy soil is maintained during the nesting period. The mud should not be highly organic or sandy. Clay soils work well.
Do not move the block once it is placed and bees find it. The Mason bee will return to the hole to build a nest for their offspring before dying.
You can be creative with your nesting blocks. Blocks can be made from any shape wood. They may be cut to a fancy shape, be a small piece of dead tree limb, fence post or scrap of firewood. You can vary the diameter of the drilled holes to attract different species of tube-nesting bees or nonsocial, beneficial wasps.
We placed our Mason bee home above the door of our barn. This way it is sheltered by the eve and will never have to be moved. We learned about Mason bees from a family member who has kept them for years. He made ours for us out of 4X6 untreated lumber.
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