An estimated 43.7 percent of the American honeybee population died in the past survey year (April 2020-April 2021). YIKES!
The stats are scary, but there’s no need to panic. You can help mitigate the loss with mason bees, a bee that’s 90 percent more successful at pollinating than honeybees.
Even if you haven’t a moment or penny to spare, this guide will walk you through how to raise mason bees of your own.
A Quick Bio Breakdown:
Before you get started, it's important to understand what you'll be working with. Here's a quick breakdown.
Classification: The term “mason bee” refers to any bee of the family Megachilidae and genus Osmia. They’re called mason bees because they act like masons, using mud to build and protect their nesting cells.
Biodiversity: Mason bees make up about 140 of the approximate 4,000 bee species native to North America. Around 500 species have been identified worldwide.
Habitat: Mason bees are found mostly in temperate habitats within the Palearctic (Eurasia, north of the foothills of the Himalayas, and North Africa) and Nearctic (most of North America) zones. However, except for Antarctica, they are found just about everywhere.
Bee-havior: While honeybees are eusocial, meaning they live in colonies, mason bees are solitary, meaning they live alone. In part because they don’t have a colony to protect, they are far more docile than honeybees. Only the females can sting, and it’s quite uncommon.
Raising Mason Bees:
Mason bees are native bees, so unlike honeybees, there’s no need to buy them. To raise them, simply build a proper home, and attract them to it.
Building Your Mason Bee House:
In nature, mason bees nest in abandoned tunnels made by wood-boring insects. They prefer tunnels that are slightly bigger than their bodies.
To mimic this, you’ll want to build a house with tunnels, called nesting tubes, of a 3/8 in diameter. This size provides just enough room for the biggest mason bee species, while still being snug enough for the smallest.
Option #1: Tightly pack an unwanted mug with paper straws (or rolled magazine pages) of a 3/8 in diameter. Trim the straws to be 1/8 in shorter than the lip of the mug. This option is the quickest, cheapest, and most kid-friendly.
Option #2: Spacing them about 7/8 in apart, drill 3-6 in deep tunnels of a 3/8 in diameter into a solid wooden post. Use scrap wood to make a roof. Any type of untreated wood will do; however, red cedar can help attract the bees and ward off pests. Tuck paper straws (or rolled magazine pages) inside each tunnel. This option is the most sustainable and attractive.
Installing Your Mason Bee House:
To install your mason bee house, securely mount it to a wooden post outside, facing Southeast, 1-6 ft from the ground. If you don’t have a post, consider taking advantage of trees or stable structures around you, like sheds and fences. Store your nesting tubes separately from your mason bee house in a cool, dry space. Tuck them back into your mason bee house in late February, or just as wintry weather is about to end in your area. Around the same time, if no natural mud source is available near your mason bee house (ideally, within 300 ft), dig a shallow hole, line it with plastic, and fill it with mud.
Attracting Mason Bees:
In the early spring, mason bees will emerge in your area, and the females will begin searching for tunnels to nest in. You can increase your odds of them picking your nesting tubes by ensuring that there are ample early-blooming, bee-friendly flowers near your mason bee house (ideally, within 300 ft).
Within one of your mason bee house’s nesting tubes, a female mason bee will use mud to build several nesting cells, each packed with one egg and enough pollen and nectar for the larva to eat. She’ll build about two cells a day, until the tube is full, and seal the tube with a thick layer of mud for protection. She’ll then move on to another tube, repeating the same process, until she has laid about 15-20 eggs in her six-week-long lifetime.
The Lifecycle of Mason Bees:
A few days after an egg is laid, the larva hatches and spends about 10 days eating the nectar and pollen inside its nesting cell. Once it’s finished, it spins a cocoon and pupates within the cell, wherein it grows into an adult by the end of the summer. It stays in the cocoon throughout the winter and emerges in the early spring. Male mason bees, which are typically located in the outer cells of the nesting tubes, emerge first. A few days later, the females follow; they almost immediately mate and, within 3-4 days, begin preparing for the next generation of mason bees.
Caring for Your Mason Bees:
Mason bees have been taking care of themselves for thousands of years. However, if you’re serious about growing their populations, you’ll want to help protect them from predation and parasitism. Here are a few approaches worth considering:
Level #1 (Least effective, least involved): Cover the front of your mason bee with hardware cloth, and remove it in time for the mason bees’ emergence in early spring. Once they have emerged, quickly replace the used nesting tubes with new ones, before the next generation settles in.
Level #2 (Most effective, most involved): Wait until late summer or early fall, to give the larvae time to grow and pupate, and remove the nesting tubes from your mason bee house. Gently tear the tubes open and remove the cocoons. Place the cocoons inside a clean box, and store them in a refrigerator at 35 to 40 °F and 50-70 percent humidity. If you store them in the same refrigerator as your produce, open the refrigerator regularly. Produce generates ethylene gas as it ripens, and too much can kill your bees. If you‘re storing your cocoons properly, they should always look pale grey and soft. If they get moldy, don’t throw them out; find a tutorial online to learn how to treat them.
In the early spring, tuck each cocoon into a new nesting tube. Then, place your nesting tubes back into your mason bee house outside (because a mason bee population generally doubles each year, you might have to install another mason bee house to make room). They’ll soon emerge on their own. If you need to expedite their emergence, you can incubate the nesting tubes at room temperature 24 hours ahead of placing them outside.
Print this Guide:
For easy access and sharing, we've created a printable pamphlet that you can download below. For the best layout, tell your printer to "print on both sides" and "flip on short edge."
With this guide, you’re on track to successfully raise mason bees of your own. If you have mason bee questions or photos you’d like to share along the way, we encourage you to reach out to us!
The Bee Informed Team. “United States Honey Bee Colony Losses 2020-2021: Preliminary Results.” Bee Informed Partnership, 23 June 2021, beeinformed.org/2021/06/21/united-states-honey-bee-colony-losses-2020-2021-preliminary-results/. Accessed 28 July 2021.
Bekey, Ron. “Orchard Mason Bees.” Washington State University, 22 Mar. 2012, s3.wp.wsu.edu/uploads/sites/2053/2017/01/Orchard-Mason-Bees1.pdf. Accessed 28 July 2021.
Hunter, Dave, and Jill Lightner. Mason Bee Revolution: How the Hardest Working Bee Can Save the World One Backyard at a Time. Skipstone, 2016.
Moisset, Beatriz, and Vicki Wojcik. Accessed 28 July 2021.
“Blue Orchard Mason Bee (Osmia Lignaria).” U.S. Forest Service, United States Department of Agriculture, www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/mason_bees.shtml. Accessed 28 July 2021.