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Mason bees in a honey bee hive

Mason bees, leafcutting bees, and other cavity nesters are incredibly easy to please. The hype you hear about their tubes needing to be a specific diameter, or a special length, or placed in a particular location is mostly nonsense. Left alone in the wild (as they were for millennia) the bees find all types of cavities that please them, from beetle borings to woodpecker holes to hollow reeds. In the wild no one measures the diameter, cuts them to length, or holds them parallel to the ground. We humans can be terribly self-important.

But just like everyone else I have neat rows of little tubes—paper straws in empty vegetable tins—and the bees certainly use them. A tin full of straws takes about three days to fill at the height of orchard bee season. These early bees are followed by other types of masons and leafcutting bees, all angling for a spot in a green bean can. Luckily for them, my dog eats a can of green beans each and every day, so when a can fills up I simply pull it off the bee shelf and add another.

But the bees in the straws are the tip of the iceberg. These are the gregarious masons that like to live (it seems) on the same block as everyone else. Other individuals nest to a different drummer.

A couple weeks ago I was checking my honey bees when I noticed mason bees flying in and out of an empty hive that was sitting between two very active colonies on the edge of the woods. You wouldn’t think mason bees would go there, with the air teaming with pheromones and threatening sounds. Curious, I opened the hive and found masons actively building away. What cavities were they using? Brood comb, of course. If you think straws in a can are tightly packed, you ought to take a good look at an empty brood comb. Claustrophobia big time.

Seeing these nests reminded me that I had a section box from the previous year that held some mud nests. I went to check on the section box, which I had put outside a month ago, and sure enough two of the bees, Osmia aglaia, had already emerged. These bees, sometimes called berry bees, are active later in the season and reach their peak after the orchard masons are done for the year.

Many species of bee in the family Megachilidae nest in empty tubes and tunnels, so it is not too late to put out your cans and paper straws. Get a dog with a green bean fetish and you can keep filling cans all summer long.

Rusty
Honey Bee Suite

This brood frame was inside an empty bee hive. © Rusty Burlew.
This brood frame was inside an empty bee hive. © Rusty Burlew.
Mason bees at work in a brood frame. © Rusty Burlew.
Two Osmia lignaria at work in a brood frame. © Rusty Burlew.
Mason bees living in a section frame. © Rusty Burlew.
Osmia aglaia nests in a section honey frame. I have no idea why they all like the upper left-hand corner. © Rusty Burlew.
Plenty of paper straws. A can fill up in about three days. © Rusty Burlew.
Plenty of paper straw nests. A can fills up in about three days and then I replace it with a new one. © Rusty Burlew.

Comments

Bill
Reply

Rusty,

You stated that it takes only three days for fill a bean can with straws and then you replace it. What do you do with the can you removed?

Rusty
Reply

Bill,

I put the filled cans in my garden shed which is enclosed but cool and dry. I leave them there all winter to protect the straws from rain and birds, then I put them out in the spring. This year I was a little late and I had mason bees flying around in there, but I managed to get them all out, I think. Lesson learned to put them out before I think it’s necessary.

Barbara
Reply

As a rule, do the bees normally fill the straws out to the very end?

Rusty
Reply

Barbara,

They fill them to the outside end, but they don’t always start all the way in the back. Sometimes they do, but sometimes they start somewhere in the middle of the straw and then work their way to the outside.

Lorry Roy
Reply

I have an overwintered hive that is doing very poorly. I have only three frames of bees, there is a queen and eggs and larvae and capped brood. I’ve added a frame of capped brood, bees, eggs and larvae, but no change. Just today I noticed that the brood is being uncapped before it is viable. I see pearly white bees in the cell. What little brood there is is intermixed
with these dead white bees. What do you think is happening.

Rusty
Reply

Lorry,

I can’t say for sure from your description, but it sounds like imperfect larvae are being removed from the hive. This is generally a good thing, but if there are a lot of these, it may be the sign of an inbred queen. See “Diploid drones“.

Karen
Reply

I live in NE Ohio and every spring, it never fails, we get a warm spell in February that last several days. There is nothing blooming yet but of course my mason bees don’t know that and start to hatch.

The bees are stored in my shed during the winter. In late winter/early spring I have learned to refrigerate them until I see blossoms starting to appear. The temperature is usually 50-55 degrees or above. It’s ok if we have days that drop below that, they seem to survive as long as they have a food source. I have an old refrigerator in the garage that I use for unidentifiable objects for or from the garden. Enter at your own risk! lol

Rusty
Reply

Karen,

Thanks, that’s good advice. By the way, I have a freezer for unidentifiable objects, including all kinds of bugs, so I get it!

Myrna Warren
Reply

Rusty on a totally different subject: We have 4 honey bee hives and all are infested with earwigs in the top covers and inner cover. How can we get rid of them without harming the honey bees? They don’t seem to be inside the supers. I tried cinnamon and it didn’t work.

Rusty
Reply

Myrna,

Although unsightly, earwigs do no harm in your honey bee hive. Some say they eat small hive beetle larvae, but I don’t know if that’s true or not. In any case, you will do more harm by trying to get rid of them than by just leaving them alone. They pretty much stay in the covers where it it warm, dark and moist with plenty of small stuff to eat.

Anna
Reply

Mason bees have filled the wheel wells of my garbage bin. I will send you a picture!

Rusty
Reply

Anna,

Can’t wait to see the pics!

Anna
Reply

How can I send a picture? Is there an address I can use?

Rusty
Reply

Anna,

I just sent you an email.

Pat
Reply

I’m incredulous the bees will fill a can up in about 3 days. I’ve got drilled nesting blocks. I’m waiting over a month to get them filled with only about 6 or 7 holes in each. In a rough count you’ve got about 100 straws in each can. I like your setup. I’m going to write a short post about my Mason bees including a video of them pollinating meadowfoam (Limnanthis Douglasii)? Can I borrow that photo if I credit it to you and link it to this post?

Rusty
Reply

Pat,

Yes, you may. Thanks for asking in advance.

Marilyn
Reply

I recently ordered some paper straws to use for mason bees instead of the expensive tubes sold for them. When they arrived, I was dismayed to see how small diameter they were. Do you buy a particular brand? Somehow I thought all paper straws were created equal! The bees are done for this year, but I want to be prepared for next year.

Rusty
Reply

Marilyn,

Have you seen my straw page? I don’t know the size of your straws, but I think the cardboard tubes are too big. I prefer them smaller. In any case, I put out the tubes for summer bees at the beginning of June. The summer bees, including some types of masons, leafcutters, and ceratina prefer the smaller tubes. Some use drilled holes that are only 1/16 of an inch wide, and no way is a straw that small. So put some out in a can now, and you will get an assortment of bees.

Adrienne Welch
Reply

Hi there Rusty,

Today I passed by one of my Mason bee houses observing what appeared to be a single mason bee still hard at work late in the season here in Maryland.

I could see the black abdomen partially sticking out of one of the tubes and assumed it to be a mason bee until it began to kick bits of soil and bits of pollen out of the hole! When it finally emerged, out came a small bumble bee, Bombus impatiens. She went on to clear out another tube, kicking soil out and bringing her own pollen in!!
Have you ever seen this behavior before? My husband is distressed because he fears all the Mason bee larvae will be compromised.

What to do????
Any thoughts or insight will be much appreciated!

Best,
Adrienne

Rusty
Reply

Adrienne,

I’m afraid your bee cannot be a bumble bee. Nearly all bumble bees nest in the ground, except for a few species that nest above ground. But regardless of that, bumble bees are social insects that nest in large groups or colonies. They have a social structure which includes a queen, workers, and male bees. Because they live in a large nest with perhaps 50 to 500 other bees, they wouldn’t choose to live in a tube. I suppose it is possible for a mated queen to select a tube for overwintering, although I’ve never seen that happen.

The thing to remember is that North America is home to about 4000 species of bees, many of which look like each other. Oftentimes, it is extremely difficult to tell them apart even when dissected under a microscope, so mis-identification is common.

About 30% of all bee species will nest in tunnels and tubes, and I would suspect one of those. It could be a carpenter bee (although they usually like to dig their own holes), it could be a type of summer mason, a leafcutter, a ceratina, or a wool carder among others. I was going to say it could also be a bee-mimicking fly or wasp, although those would not carry pollen.

I sometimes see tubes dug out by other bees, but I just leave them to it, assuming that is what would happen in nature. In the past, it has only been a few tubes and I find it interesting to see what all emerges in the spring.

In any case, if you are worried about the mason bees you can put their tubes in a cool shed or garage for storage until next spring.

Adrienne Welch
Reply

Good morning Rusty,

Thank you so much for your prompt response to my mystery visitor at one of my mason bee houses! I have been watching the mason house for continued signs of this little bee and was lucky enough to spot her again backing out of one of the tubes, once again kicking out soil behind her. She flew down to a pot of lavender planted below and l managed to capture some blurry photos of her (she is a fast moving little thing)!

As luck would have it a few days later l met a friend for coffee, Sam Droege, a bee biologist from the USDA Beltsville, Maryland bee lab and co-author of a book entitled: Bees An Up-close Look At Pollinators Around The World.

Sam listened to my story then examined my fuzzy photos and identified my mystery bee as Anthophora abrupta, a mining bee closely resembling a small bumble bee. Of course he cannot be100% certain without the actual bee to examine, but feels that there is reasonable probability based on the behavior of the bee and to a lesser degree, my poor photos!

You were correct, she could not have been Bombus impatiens. I was fooled by her close resemblance to the Eastern bumble bee but did not consider how her behavior did not fit that species.

This has been a fun & interesting experience and once again l am amazed by the diversity of the bee world!!!

By the way, I am not certain if the woody shrub/tree holly berry grows in your region, but if it does do try and plant one! Mine is covered with thousands of tiny white flowers, in bloom right now and attracting so many different types of bees and wasps l cannot possibly count them all!!! So nice to feed so many mouths with just one plant!!

Thank you again for your willingness to help by sharing your extensive knowledge.

Adrienne

Rusty
Reply

Adrienne,

I have photos and a post about Anthorphora abupta, courtesy of one of my readers, Robert Lunsford.

Adrienne Welch
Reply

Hi Rusty,

I need to make a correction to my previous post.
The small tree/shrub is actually winter berry, not holly berry that l have planted in my yard. It really does seem to be a bee magnet! So sorry for my miscommunication.

Adrienne

Gretchen Ottosson
Reply

Rusty,

I love your can/paper straw set up for your mason bees. It looks like a simple and affordable way to add nesting space. I have two quick questions: Do you find it necessary to protect them from the rain? I see that you live in western Washington, so likely have the same climate that I have in Portland, OR. I don’t have a covered patio or sheltered area in which to hang a bee house. It just seems like a summer rain would harm the straws. Thoughts? Suggestions?

Secondly, you split the straws to make them easier to open up. Do you split them down their entire length, or just a smidge at one end so that you can tear them open.

Thanks for your assistance! This is my second year raising mason bees, and I’m realizing that I have much to learn still.

Rusty
Reply

Gretchen,

I mount them under the eaves of my house for rain protection, and I think it’s necessary to protect the straws or tubes. I prefer to split the straws all the way down; it just makes it a little easier.

Tom
Reply

On our apple orchard, we put up nesting blocks a few years ago. Native bees have occupied the holes. Your website and postings are quite informative for mason bees in straws. Most sites reference the nesting tubes, not straws. We’ll be anxious to see our mason bees move into the straws and will give you a report back after this season.

Rusty
Reply

Tom,

I look forward to that. I would love to know how they do. Send photos of your set-up, if you can.

Tom
Reply

The straws we got are 0.22″ ID. That seems to be too small. Will these work?

Rusty
Reply

Tom,

That is too small for Osmia lignaria. Other types of mason bees like Osmia aglaia, some of the leafcutting bees like Megachile rotundata, and other random bees will do fine in 0.22-inch tubes. Sometimes my own masons (O. lignaria) nest in 1/4-inch tubes, but it’s a tight fit. The recommended size is 5/16-inch or about 0.31 inches. If you have a variety of wild bees pollinating your orchard, I would go ahead and use some of the small straws, but I would also provide some that are bigger, say 1/4-inch and 5/16-inch. It depends a lot on what species of mason bees you usually attract. Personally, I prefer an assortment of sizes because that way you get a more natural distribution of bees and not a monoculture of any one, which can lead to more diseases and parasites.

Tom

Thank you. Great experiential advice!

Marilyn
Reply

Rusty, do you have much of a problem with parasitic wasps in your mason bee tubes? A couple of years ago all of my tubes had tiny holes in them and no bees so last year I pulled them out as they were filled and put them in a protected spot. Thought this year I’d use drilled boxes instead. Any way to keep the wasps away?

Rusty
Reply

Marilyn,

Parasitic wasps and bees are so closely related that it is hard to control them. On years when I’ve seen big outbreaks, I’ve spent hours (literally) catching them in butterfly nets. Also, as soon as a tube is filled, I remove it and place it in a fine mesh bag. Other years, they aren’t much of a problem. I think it’s best to attract a variety of tube-nesting bees by using a variety of tube (or straw) sizes. That way you spread out nesting-building over a longer period of time, which means you are less likely to get totally wiped out by one species of parasitic wasp. In nature it’s not much of a problem because the bees are distributed all over the place, and so there is not one central “egg-laying station” for the wasps to visit. But as soon as we build a monoculture, we invite trouble.

Susan F.
Reply

Something keeps pulling the straws/cardboard tubes out of my mason bee tube. Any idea what it might be?

Rusty
Reply

Susan,

Mason bees are doing it. Sometimes it’s a tight fit, and as the bees start to fly away, their abdomens are still inside the tube and tubes get pulled with the bee for a short distance. Sometimes they are just pulled a short distance and sometimes they completely fall out.

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