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Monday, October 2, 2023

How to Attract Mason Bees and Keep Them in Your Garden by Cheryl Kaumeyer Wethey

 

Note nesting tubes that are being plugged with mud. 
All photos by Cheryl Kaumeyer Wethey


Solitary Bees make up 70% of the bee population in Colorado.   Included in this category are Mason Bees, members of Osmia lignaria species.   The Mason Bee gets its name from its characteristic behavior of incorporating mud like a brick mason in building and sealing their nests. 

Mason bees are one of the earliest solitary bees to emerge in the springtime.  They are fairly easy to identify.  The Mason Bee is smaller than a honeybee, most have a metallic black, blue, or green color to their shell and females collect pollen on the scopa, or hairs, on their underbellies.  Sometimes Mason bees are mistaken for the common fly, but unlike the fly which has one pair of wings Mason Bees have two pair of wings. 

Mason Bees emerge in the spring, when the ambient temperature reaches 50+ degrees.  The males emerge first, followed by the females a few days later.  The lifespan of a male Mason Bee is 2 weeks, while the female can live 4-6 weeks.  Mason bees are generally active from March to May.  Each female is a queen and their job is to collect pollen and lay eggs.  Each queen can lay between 10-15 eggs. Once the females emerge, they begin collecting pollen and a bit of nectar.  They mix the pollen and nectar with a bit of saliva and place it in the back of an available nesting hole.  The queen repeats this process until the ball is about the size of a pea then she lays an egg on top of the ball.  The egg and food are sealed off with a thin wall of mud to protect the larvae when it emerges from pests and weather.  This process is repeated 10 to 15 times then the chamber is sealed with a thin wall of mud. When the eggs hatch, the larvae feed on the pollen and pupate inside the chamber.  The larvae survive throughout the winter in this nest, and an adult bee emerges in the spring. 

Mason bees are good pollinators, but stay close to home, foraging within a 300foot circle, providing there are enough flowers for the bee to find good pollen. 

A single Mason Bee can pollinate enough cherry blossoms to net 12 pounds of fresh cherries, while it would take 60 honeybees to do the same Job.  Mason Bees prefer foraging on fruit trees, but are also good pollinators for early spring flowers in your garden that are in bloom during their 6 to 8 week lifespan.  Native bees tend to show preference for pollinating native plants and can pollinate up to 2,000 blossoms in a day.

 

ATTRACTING AND KEEPING MASON BEES IN YOUR YARD:

 In order to encourage Mason Bees to your yard you need to provide four basic things in your garden, a nesting place, a source of clean water, mud, and flowers for food to support their population.

 NESTING: Commercial nesting boxes can be purchased or a DIY pattern is available on the Audubon website https://rockies.audubon.org/blog/naturalist/how-to-build-a-pollinator-house Nesting holes or tubes need to be cleanable or disposable and should be taken care of on a yearly basis, as Mason Bees are prone to mites and parasites.   Nesting tubes that are 5/16 “ in diameter and 6 “ deep are ideal.  Each queen occupies a nesting hole or tube and may utilize several in a season.    When choosing or making a nesting box, try to avoid leaving a space between the top row of holes and the roof to discourage wasps or birds from nesting there.

Examples of Mason Bee houses


Where you hang the nesting box is also important.  It should be hung 6 to 8 feet off the ground.  A south facing location, out of the wind is best so that the larvae stay warm in the winter, and under the protection of the eaves is preferable. 
CLEAN WATER: Mason Bees benefit from a source of clean water and a watering site is easy to create.  A shallow dish filled with water and half submerged rocks provides them with a place to land and drink.



MUD: The female bees need a source of moist mud to create the bricks for their nests.  If most of your garden has been mulched you can provide a small dish of mud near the nesting box.  Either the mud in your garden or that in the dish need to be kept moist during the females lifespan, generally March to May.

FLOWERS: Mason Bees depend on flowers that are blooming during their lifespan, which is in the early spring, generally between March and May.  Plants for early pollinators include:

  • PASQUE FLOWERS: Pusatilla patens
  • Lewis Flax: Heterotheca villosa
  • Colorado Blue Columbine:Aquilegia coerulea
  • Dandelions: Taraxacum officinale

There are 946 known native bee species in Colorado and most are solitary bees. Native bees make up about 70% of the bee population in Colorado.

To learn more about native bees, how they live, why they are beneficial to your backyard, you might consider getting involved with The Bees Needs, a citizens science project that focuses on collecting and recording data on native, solitary, wood-nesting bees and wasps.  They are located in Boulder, Colorado.

For more information about attracting Mason Bees:
Hunter,Dave and Jill Lightner.  Mason Bee Revolution:How the Hardest Working Bee Can Save The World One Backyard at a Time. Skipstone, 2016