Carpenter bees are nature's answer to the cordless drill. They are incredible drillers and cause significant damage to wooden buildings by burrowing long holes. The bees do not actually eat the wood but drill tunnels as a place to lay eggs. Their preference is to find an old hole and drill further into the wood each year before laying their eggs. Over time, the continued removal of wood causes significant damage and eventual failure of the wooden support. In the forest, bees find old dead wood to drill into and cause no harm at all. Unfortunately our homes and barns are a big target for carpenter bees with an unlimited amount of exposed dry wood for nesting. Picture 2 shows damage in a piece of lumber and picture 3 shows how extensive the nests can be in a piece of firewood.
Carpenter bee traps are not an original idea, but in searching for an instructable, I discovered no one had posted plans. Since I needed to make some traps I thought an instructable was in order. There are many designs and you can google for images to see the variety. Most of them are pretty close to this design.
Step 1: The trap is set
The trap is a simple wooden box with 1/2" holes drilled in all 4 sides at an upward angle. Since the bees prefer to use an existing hole, these traps provide the hole they are seeking. Once inside the box, the bees fly toward the light and end up in the plastic water bottle at the bottom. Two things I saw mentioned online were that these bees like an overhanging roof and a sloped side to the box. I included these design elements by providing an oversized roof and angling 2 sides of the box.
Step 2: Building the box
You can use any wood you like for the box as long as it's unfinished and not pressure treated. Carpenter bees don't like finished or pressure treated wood. I happened to have some old barn wood that wasn't good for anything else and it made for some nice rustic boxes. You need 5 pieces of wood to build the box. The large sides are 7 1/4" wide at the top, 4 1/2" wide at the bottom and around 8" tall. Mark 7 1/4" on one side of your board, set your miter to 10° and make the two cuts angled towards each other. This will give you 4 1/2" at the bottom or pretty close. These dimensions aren't set in stone so you can adjust to fit your fancy. Repeat and you have your first 2 pieces.
The third and fourth pieces serve as the other sides. They are made from 3" wide wood and it's easiest to just rip some 3" wide boards before you start. I don't have the exact measurements for the length because it will depend on how tall you are making your box. Instead, take one of the trapezoid pieces and use it to mark the length of the side pieces. Your marks will be at angles oriented in the same direction. These are also 10° cuts on your miter saw and make the top and bottom of the trap flat. Assemble your box with some wood glue and nails. Don't get your nails too close to the top if you plan to slope the roof (read on).
Picture 2 - To slope the roof a bit I tipped my miter saw 10°-15° and cut the top as far as possible. I finished the cut with a hand saw. When assembling your box make sure to keep the nails an 1" or so from the top so you don't saw them.
Picture 3 - Drill a 1/2" hole angled upward in each side near the top. The bees prefer to climb up into a hole and it also makes it harder to find the hole when they want to leave.
Step 3: Making the bottom of the box
Inside the box is our 5th piece of wood which measures 3"x3". Angled cuts (10°) are made on two opposite sides to accommodate the sloped walls of the trap. Drill a hole in the center of the block which matches the size of the plastic bottle you are using. I had a 2 1/4" hole saw and it fit my bottles pretty well although a bit small. 2 1/2" would probably be better but it's not critical as long as you can affix the bottle.
Once your hole is cut slide the bottle through, cut off the bottle and make some tabs with a sharp knife. Staple the bottle tabs to the wood and place the block inside the trap box. Picture 5 shows what the inside of the trap looks like from the top. When the bees enter the box, the plastic bottle is the obvious exit as it is the only source of light in the box. The bees fly down and enter a second plastic bottle which we will prepare next.
Step 4: Finishing the bottles
To connect the "capture" bottle with the 1/2 bottle/funnel, tape 2 bottle caps together with electrical tape or gorilla tape. Ideally it would be best to epoxy or superglue them together as that will last longer. Once the caps are affixed together, drill another hole through the caps for the bee's escape. Once you've screwed the 2 bottles together (pic 2) you are ready to put a roof on this old trap.
Update: UncleSam created an instructable on how to connect the 2 caps using a 1/2" grommet. Very nice permanent solution.
Step 5: Add the roof and you're done.
The trap needs a wooden roof with a couple inches of overhang and I used some old shingles. You can simply use another piece of board as well. Nail the roof to the top of the walls. To hang the trap you can staple a string in the center of the top, add a hook eye if you used a board, or something similar. I did something similar by drilling a hole in the shingles and passing a string out the bottle so I could tie a short dowel to it (pic 2). Since the shingles aren't super strong, the dowel disperses some of the weight to a larger area of the roof.
Step 6: Success!
Now hang your traps and catch some bees. Supposedly the corners of your house/barn/porch are the best spot for these traps. You may have to move them around a bit depending on your situation. Hopefully your traps will look like this one after a few days! Thanks for taking time to read about making bee traps. If you have carpenter bees at your house, you know you need 'em!