Mason Bees

We have all heard the term colony collapse disorder, where honey bees are disappearing. Honey bees are not the only ones afflicted. All pollinators are suffering from the loss of habitat, mono-cropping, disease, etc. Pollinators like bees are responsible for pollinating 30% of the World’s crops and 90% of wild flowers. Sadly, the honey bee gets all the attention when it comes to news stories. Don’t get me wrong I love the honey bee and keep some bees myself, but mason bees are the true heroes. Mason bees are just a small subset of over 4,000 species of native bees in North America. Honey bees are in fact not native to North America, but were introduced here from Europe.

What are mason bees?

Mason Bee on Yellow Flower

Blue Orchard Mason Bee

Mason bees are a solitary bee from the family Megachilidae. The Megachilidae family is a cosmopolitan family meaning the different species in this family are spread world wide. Megachildae family is made up of the genera of the mason bees and leafcutter bees. They get their name from how they build their nest cells, soil or leaves respectively. The main characteristic of this family is the fact that they have their pollen carrying structure (scopa) on their abdomen, as opposed to being on the hind legs like we see in the honey bee. Within the family Osmia all the females are fertile and there is no caste system like there are in honey bees. In the United States there are two common species of mason bee, the ranges of these bees are separated by the rockies. The western subspecies is Osmia propinqua, and the eastern subspecies is Osmia lignaria.   Mason bees make their homes in hollow reeds or in wood made by wood-boring insects; like that hole that the carpenter bee made in your deck last year. Unlike the honey bee, mason bees make no honey or beeswax. Research is currently being conducted to use the mason bee to pollinate commercial crops. Honey bees are effective pollinators, and common in commercial pollination, but the native bees like mason bees are much more efficient at pollinating.

Mason Bee’s Life Cycle

Cluster of Mason Bee Cocoons

Mason Bee Cocoons

The mason bee’s adult life begins in the spring when they emerge from their nesting tunnel. Inside each nesting tunnel their are 5 to 6 cocoons with full grown bees. When the daytime temperature reaches 57 degrees the bees begin to emerge from the cocoon. The males cocoons are near the front of the nesting tunnel and emerge first and don’t wander far from the nests so they can mate with females as they emerge from their cocoon. It is not uncommon to see a ball of mason bees on the ground after a female emerges. This is male bees battling for a turn to mate with the newly emerged female bee. After all the females have been mated the males die. This is a common them among bees. Even in honey bee hives drones (male bees) are only allowed in the hive as long as resources are available. Otherwise, they will be drug out of the hive and will starve. The females begin foraging for nectar and pollen, while waiting for her ovaries to mature.  The mason bee will not excavate their nest. they will only nest in tunnels that are already hollowed out. Whether it be a mason bee house or a hollow reed. A female mason bee may inspect several potential nests before settling on the perfect nest. She will then do an orientation dance/flight to visually orient herself with her hive and landmarks around the hive. After finding the perfect nest the female mason bee will set out to collect pollen and nectar, and other nest making materials. Nest making materials when talking about mason bees is a euphemism for mud. Unlike the honeybee who is willing to travel out from the hive in a 5 mile radius, mason bees prefer to stay close to the hive. One bee will visit 75 flowers per trip and it takes upwards of 25 trips to gather enough pollen nectar provisions for one egg. That means just to lay one egg the mason bee has visited around 1,875 flowers.  She will pile the pollen and nectar she collected in the back of the nest. After collecting enough pollen and nectar, she will back down the nesting tube and lay an egg on top of the nectar/pollen pile. The pollen and nectar serve as sustenance for the baby bee. The mason bee then partitions off that cell with mud and begins the process of collecting nectar and pollen again to create another pile of nectar and pollen. She will fill out the nest partitioning off cells that have an egg, along will pollen and nectar. Typically, female eggs are laid at the back of the nest and male eggs towards the front. When the female mason bee lays eggs she will fertilize female eggs, and not fertilize male eggs, similar to what the honey bee does when laying eggs. Each tunnel will typically have 5-6 individual cells each containing an egg. After filling out a nesting tube, the female will search for another nesting tube to fill. She will work tirelessly for 4-8 weeks continuing this same process, until she dies. On average a mason bee will have filled 4 nesting tubes, and have visited nearly 60,000 blossoms. When the mason bee egg hatches the larvae will consume the food provisions provided by its mother. After consuming the pollen and nectar the mason bee larvae will spin itself into a cocoon and enter the pupal stage. During the fall and winter the mason bee will mature and hibernate while waiting for the spring. The young mason bee will spend most of its life alone in the small nesting cell its mother created for it. Once spring comes and the temperature is consistently about 57 degrees the cycle begins again.

Providing Habitat for Mason Bees

Mason Bee Tunnels

Mason Bee Nests

Providing habitat for mason bees brings many benefits. They are extremely efficient pollinators. 250-300 female mason bees can pollinate an acre of flowers. Unlike honey bees most mason bees that you will see in your garden are native to North America. Mason bees rarely sting, only stinging in cases of being stepped on or squeezed. Unlike honey bees, mason bees only require small mason bee houses. With these small bee houses you can get into backyard beekeeping at a fraction of the cost and time it takes to keep honey bees. To provide habitat for the mason bees all you need to do is provide them a house and they will do the rest. The bees prefer a tunnel 5/16 inch in diameter. Ideally, the tunnels should be six inches. Six inch deep tunnels allow for a better ratio of female bees and encourage growth in your native pollinator population. Mason bee houses come in many different beautiful designs. This allows you to pick a bee house that matches the decor of your garden. This will allow the bees to be right at home in their new house and their house right at home in your garden. You will want to mount your new mason bee house five to seven feet off the ground, facing south or south east so they get early morning sun. This early morning son is like a cup of coffee to us, it helps them kick start their day. The bees will prefer to have spring blossoms close by so that collecting pollen and nectar is easy for the bees. Also, you will want to attempt to place them close to a source of clay mud if possible making nest construction easier.

Mason Bees Pollination and Commercial Use

When the mason bee lands on a flower to collect nectar the pollen from the flowers stamen will be collected on the hairs on the bees body. She collects the nectar with her proboscis which is like a tongue. When she flies to the next flower the carpel or pistil of the takes some pollen from her body to fertilize a potential seed, and that flowers stamen leaves pollen on her body. Due to the mason bees early emergence in the spring when honey bees may not yet be active they are popular for pollinating early blooming fruit orchards like cherry orchards. Also, mason bees have an affinity for these fruit flowers. Researchers and farmers are experimenting with and using more mason bees to supplement the dwindling supply of honeybees available for pollination. It is an interesting trend to see the farmers working with the bees to encourage the native bee population. The trend is moving towards a more sustainable model of agriculture and pollination. Farmers that are interested in using mason bees for commercial pollination need to set out enough nesting sites to support the 250-300 bees per acre of orchard. They will then source mason bee cocoons from online too seed these nests. During the fall the farmers will store these full nests in a nice cool dry place protected from pests, and set the nests back out in the spring to repeat the process.


The mason bee is the unsung hero of the beekeeping world. As the world searches for answers to the varroa mite epidemic and the colony collapse disorder these small solitary bees are swinging above their weight to help pollinate our world, and keep or food supply open. These small bees will be a great and sustainable addition to your garden with a fraction of the costs and time that honey bees take. You saw it here first folks these bees are going to be extremely important and well known in the near future. Be a trendsetter and start keeping mason bees and native pollinators close.