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Fall Care for Mason Bees

10/7/2016

20 Comments

 
We've received many requests from people for more info on mason bee care. While we don't currently have live stream capabilities for sharing our in-person workshops, we can write how-to's! If you are local to Squamish or the Lower Mainland, stay tuned for more workshop dates in the spring and fall. We hope this post is helpful for keeping your mason bees happy and healthy. ​
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What are mason bees? 

Mason bees are a group of bees in the Osmia genus. There are 140 species in North America, about 60 in BC! They are solitary, meaning that they don't live in a colony with other bees (unlike honey bees which live in colonies of 50-100,000 individuals). Instead, the male and female mason bees live and work alone, except for mating. (See lifecycle diagram below.) Mason bee females may nest together in mason bee homes we provide them, but they don't really interact with each other. 
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How to identify mason bees
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Mason bees are easy to miss- they look a lot like houseflies. They are usually dark and metallic blue/green around here, although they have longer bodies than houseflies and more distinct body segments (head, thorax, abdomen). Their bums are more rounded or "bullet-shaped" than other solitary bees that may look similar. A tip for telling flies apart from bees is flies have big bulgy eyes on the tops of their heads, while bee eyes are smaller and on the side of head (not counting honey bee drones). Flies have 2 wings, bees have 4. Another mason bee characteristic is they are only around in the spring- approximately from late February to June. The adults die after that. For that reason, they are great pollinators for early flowering crops, like fruit trees.
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Mason bee female (Osmia lignaria)
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This is a fly. Note the large eyes, short antennae, and only 2 wings.
The males are smaller than the females, have longer antennae, and often have fuzzy blonde moustaches- no joke!! The males can't sting, and while the females can sting, it's unlikely. ​
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Look at that moustache! Photo credit to http://blueorchardmasonbees.yolasite.com/
How do I "keep" mason bees? 

Mason bees do not require extensive maintenance like honey bees. You can simply buy or make a mason bee home (lots of style options, but make sure you can take the whole home apart to access cocoons in the fall, or use paper tube liners in drilled holes), mount it outside in late February/March, and wait for wild mason bees to find it. They will get busy laying eggs in the home, and then it's your job to clean the home in August-October, and store the cocoons over the winter to keep them safe. 
Why do I need to clean the cocoons and mason bee home? ​In nature their cocoons wouldn't get cleaned! 

​When we put up a mason bee home, we are encouraging the bees to lay a bunch of eggs very close together. In the wild, the bees would be forced to lay a few eggs over here in a hollow stem, and a few over somewhere else. With many nests together, it's easy for parasites to locate them and move from one nest tube to another. Your whole mason bee home could become a breeding ground for parasitic wasps, pollen mites, fungi, etc. over the winter (see photos below). So because we are setting up these unnatural situations, it's important for us to be responsible and give the bees a hand, so we don't do more harm than good. 
​
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Parasitic wasps in a cocoon we found this week. Dead adults below, live developing larvae in the cell.
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This is what you might find inside your mason bee home when you open it up in the fall.

How to Clean Mason Bee Cocoons


1. REMOVE COCOONS
Open up your mason bee home or pull out and unravel the paper tube liners. (The brown stuff that look like mini chocolate sprinkles is bee poop (frass), the yellow/orange sticky stuff is pollen, the light brown/reddish stuff that moves slowly are pollen mites.)

If you have a tray/routed house design, scoop out cocoons gently using a chopstick or tool designed for this purpose. Float the cocoons in a bowl of cool water.


​2. CLEAN 
Gently roll the cocoons with your fingers to clean off frass etc. You can also use an old toothbrush to gently scrub the cocoons. Cocoons can stay in water for up to an hour, but I usually only soak for a few minutes. Inspect cocoons for holes. If they have a tiny hole in them, parasitic wasps have gotten in, and the bee is dead. Cocoons that sink are dead- you can discard them.



3. DISINFECT 
Scoop up cocoons and float in a bowl of 1L (4 cups) cool water and 1 tsp hydrogen peroxide or bleach. Swirl the cocoons around and let soak for a few minutes. This kills off any fungi and bacteria on the cocoons that could infect them later. Afterwards, disinfect the mason bee home by soaking in the solution for 15 minutes. 



4. RINSE 
Rinse the cocoons throughly. I do this in a sieve under cool running water. 



5. DRY 
Place your cocoons on a clean tea towel to dry. Roll them around a bit then let them air dry for a few hours. 



6. STORE 
Layer cocoons and crumpled up paper towel in a glass jar with many holes punched in the lid. The cocoons want to be dry and have air circulation so mould doesn't develop. Put the container in the fridge, or in an unheated garage or room. Monitor them for signs of mould. They want to be at about 60% humidity, and above freezing. Some say that fridges can be too dry for the cocoons. Try storing cocoons in a few different locations you have available and compare their hatching rates-then you'll know the best storage location for next year.



7. HATCHING 
In the spring, when temperatures are about 12*C, and fruit trees are about 25% in bloom, bring your cocoons outside and place them in an open container in the sunshine. We tack a shallow yogurt container to the side of our house on the south side, beside our mason bee home. The males emerge first, and do not sting. The females emerge a few days or weeks later. 


Where to put your mason bee house
  • In a sunny location. South or East facing is best to get morning sun. This helps the bees get moving early in the day. 
  • Head height so you can see what’s going on, although the bees aren't picky about height. 
  • Protected from wind and rain. 

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A pile of pollen mites. They move so slowly that you may not think they are moving at all at first glance.
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This poor bee is emerging from a nest FULL of pollen mites. The bees can still survive, but it impacts their health over time. This mason bee home hadn't been cleaned in years.

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Step 1: Remove cocoons and float in cool water
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Step 2. Gently remove frass by rolling cocoon between fingers or using a toothbrush
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Step 3. Disinfect cocoons
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Step 5. Air dry for a few hours
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Step 6: Storage. Lots of holes poked in lid! Image from http://www.davidsuzuki.org/
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Step 7: Hatching. Our high tech setup for emergence in the spring. We tack a shallow container to the side of our house just underneath our mason bee house. If it rains, it will stay dry, but it gets southeast sun to warm the cocoons in the morning. Avoid windy areas. You could put some wire on top to keep birds out if necessary.
20 Comments
Denise
9/25/2018 10:37:31 am

Hello,
I have a bee house with bamboo tubes attached to a tree facing East. Some holes have been plugged up with mud. It is almost October - what do I do with the bee house in the winter? Should I take it in? I would like to protect those bees and the cocoons. Help. Thanks.

Reply
Kari
9/22/2019 11:43:54 pm

I also have the tubes? How do I get the larvae out of the tubes or should I? I don't want to damage the cocoons.

Reply
Michalina Hunter
4/16/2023 03:45:00 pm

Hi Kari,

If you have bamboo tubes, you wont be able to open them up and clean the cocoons without damaging the larvae. If you have cardboard or paper tubes, you can unwrap the cocoons for cleaning.

We don't recommend using bamboo tubes because they last a long time and diseases can build up in them over time. The easiest management technique I can recommend for bamboo tubes is to only bumble them together in groups of 10 tubes or so, and space them out in your landscape. That way if pests do build up, they won't have access to a ton of bees. And also if the tubes are not protected from rain they will break down a bit quicker- which is good!

Hope that helps.
Michalina

Michalina Hunter
4/16/2023 03:42:06 pm

Hi Denise,

You can move the nest to an unheated garage or somewhere cool. Or leave the nest outside- the bees will be fine!

Cheers,
Michalina

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4/1/2020 09:48:46 pm

Have you ever had issue with birds or other animals eating the cocoons while in your high tech emergence center? It seems very exposed.

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Michalina Hunter
4/16/2023 03:40:44 pm

So far no. They are generally pretty quick to emerge

Reply
Paul suffredin
9/11/2021 04:45:14 pm

I am new to mason bees.I see different thought patterns on keeping the bee’s in a refrigerator over the winter. I live in the Midwest outside Chicago. Is it possible to leave the house alone and outside for the winter?

Reply
Hugh Cartwright
9/18/2021 01:20:31 pm

I live in Canada's Pacific northwest, so enjoy a very different climate to you. However, I assume that the bees you have bought/been given are those that are appropriate for your part of the world, and so would survive your cold winter. There are Mason Bees in the wild in Ontario, and they seem to be fine outside, so unless you've got bees shipped in from some much warmer part of the country I'd say they would be ok outside. Perhaps you can divide the cocoons into two lots and have half outside while the rest enjoy the warmth of your fridge over the winter, then see which half show a higher success rate when spring comes.

Reply
Dennis Dowdy
10/30/2021 10:51:12 am

Hello
From what I have read mason bees in my area near Seattle, Wa would not be present at this time of the year. I would not expect to see them, but for the past two months I am seeing some flys on my south facing wall that have unusually metallic blue stomachs and wide wing spreads, making me think they are mason bees. I took some pic this AM. My questions are:
1. Where can I send pics for ID?
2. At what time of year should I clean my mason bees houses?
3. Can you tell me if my pics are flies or bees?

Reply
Michalina Hunter
4/16/2023 03:40:11 pm

Hi Dennis,

1. I recommend uploading photos to iNaturalist for ID.
2. Clean mason bee houses in the fall.
3. Flies have big eyes, very short antennae, and 2 wings instead of 4.

Hope that helps!

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Ganesh link
4/21/2025 02:18:29 am

One sting can cause a lot of pain and allergy. Covering the whole body with protective dress and wearing an full face mask is needed. Better to go with pest control services company. Just spending a few money will make the work done.

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    Michalina and Darwyn are beekeepers on Vancouver Island, BC, Canada. 

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