attracting wild pollinators

Emergence box vs hatching box: what’s the difference?

hatching box

Sometimes I use the wrong word. Yesterday, when someone asked, “What’s a hatching box?” I felt sheepish. I should have written emergence box in my post on lovage. Here’s the question:

I planted some lovage, and I too thought the stems would make good nesting tubes. So now I must ask, what is a hatching box?


What’s a hatching emergence box?

An emergence box is used for cavity-nesting bees such as mason bees and leafcutting bees. It is simply an empty box with a lid you can open. In the center of one side is a small hole, big enough for bees to pass through.

To understand the purpose of an emergence box, you need to look at the behavior of cavity-nesting bees.

Tubes and tunnels

Cavity-nesters are the bees that nest in holes bored into wood or in empty reeds and hollow stems. The female lays her eggs, one at a time, by starting at the back of the hollow space and working toward the opening. These bees usually partition the space between each egg.

In nature, these convenient nesting spaces don’t last very long. A tree with many cavities drilled by birds or beetles will eventually rot and fall. Reeds and hollow stems, such as raspberry canes or teasel stems, collapse after a season. This constant destruction of nesting sites means wild bees are always looking for new ones.

New sites are best

If the opportunity exists, cavity-nesters will nest in the same tunnel they emerged from. But if they use the same tunnels year after year, parasites, predators, and disease organisms multiply. Eventually, the nesting environment becomes so unhealthy that the baby bees can’t survive. But natural housing rots and falls apart, so it forces the bees to find new clean homes. Nature’s way works.

In the meantime, beekeepers offer these bees sturdy homes made of drilled wood, bamboo tubes, or other materials that can survive year after year. Predictably, the parasites, predators, and pathogens thrive. In fact, because of the lack of social distancing in beekeeper-provided housing, the pest populations can explode. After a few successful years, some keepers lose all their wild bees to things like parasitic wasps, pollen mites, molds, and fungi.

Enter the emergence box

With an emergence box, you can force your bees to use new tubes instead of the old ones. It works like this:

Bees prefer nesting tubes bathed in sunlight. They don’t like to go into dark places to look for a nesting place. Most won’t do it.

An emergence box takes advantage of this preference. Simply mount your fresh new housing and put the emergence box nearby with the hole facing the sun. Then put your cocoons—or even full tubes of cocoons—in the box. As the bees emerge within the dark box, they will see the dot of sunlight and fly outside for eating and mating.

But when it comes time to start nest building, they will not want to go into the dark interior of the box to find their old nesting tube. Instead, they (usually) select the shiny new tubes you have prepared for them.

I say “usually” because occasionally you will find a bee that insists on defeating your plans and nesting inside the dark box. There’s nothing you can do for these outliers; some kids are a mess from day one.

Designing an emergence box

Wooden boxes work best, but you can also use cardboard if the box won’t get wet. I like to use an empty honey super with an entrance hole drilled in one side. Then I add a bottom board and a lid.

Place your emergence box next to your nesting tubes, the closer the better. The single hole should face south or southeast and receive unobstructed sunshine. Once all the bees have emerged, you can remove the box.

Hatching is different

Larval bees hatch from eggs, but adult bees emerge from cocoons. Because you will fill your box with cocoons, the bees coming out will be adults. For that reason, the phrase “hatching box” is technically wrong and I should have said emergence box.

Honey Bee Suite

Sometimes I use an empty honey super as an emergence box. In this photo, the upper box isn't necessary, but I put it there so the lid wouldn't shade the opening.
Sometimes I use an empty honey super as an emergence box. In this photo, the upper box isn’t necessary, but I put it there so the lid wouldn’t shade the opening. Photos by Rusty Burlew.
Cardboard containers make great emergence boxes. Just punch a hole in the box, making sure the layer of cocoons doesn't cover the hole.
Cardboard containers make great emergence boxes. Just punch a hole in the box, making sure the layer of cocoons doesn’t cover the hole.

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  • Thank you. I have some condos made from drilled boards. They are Melanosmia bees, smaller than blue orchard bees and the old house was drilled with smallish short tunnels compared to the standard mason bee hole. I put it out next to the shiny new WeeBeeHouse I purchased. The bees preferred to reuse the old condo I was planning to retire. I think the width of the hole was part of the problem, or maybe they thought the too new linseed smell too strong?

    Next year I will put the entire old condo into a box and see if that stops them from coming back. Hope that works!

    • Lisa,

      It could also be some kind of pheromone. Bees seem to prefer used housing, which is why sometimes we need to trick them into using the new stuff. I find that putting entire condos into an emergence box helps a lot, but some stubborn ones will always go into the dark box.

  • Hi Rusty,

    Every year I use both drilled blocks and tubes for mason and leafcutter bees. This past spring I put the blocks in a cardboard box with a couple of pencil-sized holes and a bunch of new tubes on top of it. Guess what? The bees emerged and started going back in right away! This seemed so continuous that I never felt it was time to remove the cardboard box of blocks. This continued through the leafcutters. So now I have blocks full of bees again. Guess I’ll have to try something different next year, huh?

    • Marilyn,

      You can try turning the emergence box so the holes face away from the sun, but keep the new tubes facing the sun. Although the bees may emerge a few days later, it may be worth a try.

  • Enjoy your newsletter and this post as well! We made our first box last year and have some renters!! We will definitely follow your advice to replace the nesting medium each year. This made me wonder…when will our bees emerge? We live in southern NH close to the coast zone 6A. Also, what is the approximate date range for nesting to start? Any help or references are greatly appreciated!!

    • Pam,

      Emergence and nesting vary according to the species and to local conditions. The easiest way to estimate emergence this year is by the nesting behavior last year. It happens fast, so as soon as they emerge they begin to nest. If your renters appeared last year in, for example, April, expect to see some action at about that time.

  • Just found this website — VERY informative! It has taught me a lot but I have a lot more to learn! You wrote above: “Place your emergence box next to your nesting tubes, the closer the better. The single hole should face south or southeast and receive unobstructed sunshine. Once all the bees have emerged, you can remove the box.”

    Q: How do I know when all of the new bees have emerged?

    I first began trying to attract mason bees a couple of years ago using hollow plant stems such as cup plant and others gathered from a nearby prairie inserted into coffee cans (open at both ends — is that right or wrong?). I had immediate success! But never could figure out when to take them down or replace them as the activity in spring is always fast & furious! I didn’t know about an emergence box. Likely too late for this year as the “traffic” at my nests has been high over the last 7-10 days or so (until the sudden return of below-freezing nighttime temps). I have noticed that the bees seem to wait until the sun hits the nests before there is activity. I have the nests suspended about shoulder-high, under the overhang of my garden shed that faces SW, the only place available, really, to put them. And the bees certainly do come! I live in central Ohio. I’ll keep reading through the information & comments on this website to learn more.

    • Carol,

      If you only store the cocoons, then it’s easy to tell. But if you’re storing the cocoons still in the tubes, just wait a while. As you said yourself, the activity is fast and furious because they all emerge at about the same time. If you are unsure if a particular tube is empty, you can stick something down there to see if anything else is inside. I use a blade of grass because it won’t damage anything, yet you can see how far it goes in.

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