How to build a bee block

Of all the bees native to North America, about 30% use some kind of tunnel in which to lay their eggs. The diameter of the tunnels, as well as their preferred length, varies with the different species of bee. So, to attract a wide variety of native bees, it is best to use a wide variety of tunnel sizes.

The most popular bee tunnels range from about 3/32” to 3/8” wide. The narrower ones are usually shorter (about 3-5 inches) and the wider ones are longer (up to 6 inches). These numbers are not exact, so approximations work fine. The tunnels are easily made with a long drill bit in blocks of dimensional lumber or in the ends of bucked logs. Three important points:

  • Use untreated wood
  • The tunnels should be as smooth as possible
  • The holes should not go completely through the wood (one end remains closed)

Although most native bees are solitary in the sense that one female raises a family by herself, the members of a species like to live near to one another. For that reason, you should group tunnel sizes together. In other words, one block may have lots of ¼-inch holes, while the next block has lots of 3/8-inch holes. Space the holes at least ½- to ¾-inch apart—the larger the holes the bigger the spacing.

If at all possible, line the holes with paper straws or rolled wax paper. A paper liner does two important things:

  • It keeps the inside of the nest smooth and snag-free
  • It can be replaced every year, thereby reducing the accumulation of diseases and parasites.

The paper tubes can be gently withdrawn at the end of the season and stored in a cool dry place. Alternatively, the cocoons themselves can be taken from the paper and stored separately. In the spring, the paper tubes can be hung near the nests or the cocoons can be put in an open-ended container—like a pvc pipe or a small flower pot—from which the bees will emerge.

Hang your bee boxes at least three to four feet off the ground so they don’t disappear among the weeds and to keep them away from splashing water and small animals. Early morning sun is okay, but the boxes should be protected from direct afternoon rays. Additionally:

  • Add a small overhanging roof to keep out the rain
  • Mount the boxes on a steady structure rather than one that sways in the wind
  • A loose covering of wire mesh (like chicken wire) can help deter hungry birds in winter

That’s really all there is to it. For maximum protection against disease build-up, boxes can be sanitized with bleach at the end of the season or replaced altogether after two or three seasons. In any case, always use liners for best results.

Rusty
HoneyBeeSuite

Nest box with ready-to-hatch straws nearby.
Nest box with ready-to-hatch straws nearby.

Comments

Glen Buschmann
Reply

Wood blocks are attractive for tunnel nesting bees but an unmaintained wood block (or any multi-year tunnel nest) becomes a pest magnet for everything from parasitic wasps to pollen mites to carpet beetles. Wood blocks are great if they are replaced/cleaned ANNUALLY. You can recycle old blocks by swapping them out every other year—in springtime the inhabited block is put in a box or bag having one exit and near a freshly drilled block. The bees will mostly use the clean block and at the end of the season (June for Mason Bees) the dirty holes in the “old” block can be drilled out clean. I prefer drilling in June, because at this point any new inhabitants that did sneak into the old block are in egg and larval form and I feel less guilty for their destruction.

If you want to line the tubes, try typing paper, adding machine tape (no carbon), or brown wrapping paper; wax paper and parchment paper I have found do not hold up very well. Avoid plastic coated papers or plastic straws: not only is it more difficult for bees to attach mud to plastic, moisture builds up and mold subsequently grows on the frass (poo) and old pollen that surrounds the cocoons in the tunnel nests.

Xerces Society has some good suggestions for other types of housing and habitat—http://www.xerces.org/fact-sheets/ —as does this link on our blog—http://olypollinators.blogspot.com/p/housing-mason-bees.html

Rusty
Reply

See for more information about pollen mites and a photo of an infested mason bee.

Glen Buschmann
Reply

Feel free to send me any information you have on Chaetodactylus (pollen mites). I am organizing some students to help me research a puzzle regarding them over the coming year. If all goes well we’ll have something more to share by this time next year.

Maxwell Roswell
Reply

Your bee block looks amazing. I can’t wait to tackle this project too. I hope it’ll look good as yours and be as effective too.

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