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Nests For Bumble Bees
Click here to download a PDF of this information sheet.
Written by Matthew Shepherd and Mace Vaughan, The Xerces Society.
A Brief History of Artificial Bumble Bee Nests
The history of artificial bumble bee nests goes back at least as far as the
spring of 1887. It was then that the British naturalist John Hunt dug holes,
filled them with moss, and covered them with paving stones. A couple of years
later, another British naturalist, Frederick Sladen, began making nests, too.
He dug holes a foot deep and covered them with a paving stone or metal plate.
Sladen made entrance tunnels for these that were about eighteen inches long
and sloped upwards to emerge in a patch of trimmed grass. In later years he
began experimenting with other ways to make nest chambers-such as by burying
tin cans-and tried a variety of nesting materials, including dead and half-rotted
grass, soft moss, and half-inch lengths of unraveled rope. Sladen did most of
his experiments as a boy and published The Humble Bee, his first book on bumble
bees, which included descriptions of how to make nests, in 1892, at the age
of sixteen. He subsequently went on to become one of the foremost experts of
his generation on both honey bees and British bumble bees.
By 1926, in America, T.H. Frison had also begun experimenting with ways to make bumble bee nests. Frison used tin cans with a long metal spout as an entrance tunnel, buried in the ground and with a field mouse nest inside. (In natural settings bumble bee queens often choose abandoned mice nests as they are already lined with insulating nesting materials of grass and fur.) Nearly half of his nests were occupied. While doing this work he discovered the importance of careful siting of the nests. Queens seem to like nest sites close to obvious landmarks such as fences, distinctive rocks and logs, or trees, which they and subsequent generations from the nest use to find their way home after foraging.
In the decades since this early work, researchers have realized that artificial nests do not have to be underground. Nowadays, most artificial nests are simply wooden boxes placed above ground, and bumble bees used as pollinators in commercial glasshouse usually are housed in cardboard boxes. When choosing a nest site, a queen is looking mainly for a safe, enclosed space protected from the weather, something that can be provided in a nest easily constructed from lumber. (Also, she doesn't like working with concrete, glass, or steel.)
Making a Bumble Bee Nest
As you can tell from the above history, bumble bee nests can be made from all
sorts of materials (and some species of bumble bees will nest in unusual places),
but the majority of people make nests from wood. Unlike the nests built for
solitary bees-who can be very particular about brood hole diameters-there are
no strict size requirements for bumble bee nests. There are, however, some general
guidelines that should be followed:
· the nest should be weather tight and well insulated: the growth of
the larvae can be stunted if the inside gets too cold or, in particular, too
wet;
· bumble bees will defecate in the nest so build two chambers, one as
the brood chamber where they will make the nest and one as an entrance where
they can defecate;
· the entrance hole should be no more than ¾" in diameter,
marked on the outside with a contrasting color and provided with a landing platform;
and
· the nesting chamber needs to contain some insulating material, such
as upholsterer's cotton, dried grass, or short lengths of unraveled, soft string.
The nesting box we describe here is based on information on Tom Clothier's Garden Walk and Talk website (website link no longer available), who in turn adapted information from the B. C. Fruit Testers Association. There is an alternative design using plastic drainage pipe on the Beetools website (members.aol.com/beetools/bumble.htm).
We made a nesting box from untreated pine, with two chambers and upholsterer's cotton in the brood chamber. The description below will enable you to make a similar nesting box about 8" wide, 16" long, and 6" high. The inside dimensions of the brood chamber will be approximately 7½" by 6½" and the entrance chamber 5" by 6½". Both are 4¾" high. The dimensions of a bumble bee nest do not need to be exact. Our nest has these dimensions because they fit the plank of wood we used. You could make one of similar dimensions to fit the lumber you have. Two hours should be enough time to make this nest, after you have gathered together the lumber, tools, etc.
Materials
To make our nesting box, we used an eight feet long, 1" x 10" plank
of untreated pine, a six feet long piece of quarter-round molding (½"
by ¼"), and a piece of scrap 2" by 4". You can use any
lumber you have available and adapt the dimensions to suit the materials you
have. Do not use treated lumber, as the chemicals may affect the bees-the treatment,
after all, is intended to protect the lumber from insects. Also, plywood is
not as good as solid lumber because it is more difficult to clean. (Sometimes,
when plywood ages and begins to separate, the spaces between the layers create
great homes for parasites and mold.)
You'll need to cut the following pieces of lumber.
· from the 1" by 10" plank:
· bottom: one piece of wood 10" by 16";
· sides: two pieces of wood 5" by 16" (another 10" by
16" piece of wood, this one cut lengthways, down the middle);
· ends: two pieces of wood 5" by 6½" (a 6½"
piece of the plank cut lengthways down the middle);
· roof: two pieces of wood 10" by 14";
· from the 2" by 4":
· chamber divider: one piece about 6½" long; and
· from the ½" by ¼" quarter round molding:
· drip cap for the roof: two pieces 14" long and two pieces 20"
long.
In addition, the following materials need to be gathered:
· entrance tunnel: one piece of ¾" plastic pipe (schedule
40 PVC works well), about 8" long;
· two small pieces of door screen, or similar;
· upholsterer's cotton, short lengths of unraveled soft string, or similar;
and
· nails, glue, caulking, etc. to fix everything together and finish the
nest.
Tools
No special tools are needed.
· saw (for cutting lumber and plastic pipe);
· hammer or screw driver;
· tape measure and straight edge for marking the plank;
· drill and bits (1", ¾", 1/8");
· stapler; and
· miter box (not a necessity, but ideal for cutting the molding for the
drip cap).
We used glue and nails to fix together the pieces of lumber, although, if you prefer, you may use screws. The screen was stapled in place, and the plastic entrance tube was a friction fit.
Directions
(Click HERE to see a slide show
of images to help you construct a nest box.)
1. Sides and bottom Assemble the sides and ends to form a top- and bottom-less
box (have the narrow ends sandwiched between the longer sides), and then attach
this to the bottom piece you cut. The box should be flush with the edge of the
bottom on three sides and have a landing platform about 1¼" wide
(defined by how wide your plank or lumber is) along one long side. This will
be the front of the nest.
Drill a few small-diameter ventilation holes through each end panel close to the top. Cover these on the inside with the door screen to discourage ants.
2. Interior divider Cut the 2" x 4" to length so that it just
fits from front to back across the interior of the box. This will create a chamber
divider about 2" thick and 4" high, with a 1" high gap between
the top of the divider and the roof. Drill a ¾" diameter hole through
the divider, about 1" from the back of the nest and close to the bottom,
to create an access tunnel for the bees between the chambers. Fix the divider
into the nest box to create one chamber (brood) about 7½" by 6½"
and a second chamber (entrance) about 5" by 6½".
3. Entrance tunnel The entrance tunnel should go through the front panel of the nest into the entrance chamber, and end close to the access tunnel through the internal divider. Drill a 1" diameter hole (or whatever size fits your pipe) close to the bottom of the front panel of the entrance chamber. Cut the pipe to the correct length and insert it into the hole. It should be a tight fit in the hole (you might need glue or caulk to hold it in place). On the outside, highlight the entrance with paint or similar (a permanent marker will do) as a landmark to help bees locate it.
4. Nesting material Place a small amount of nesting fiber (upholsterer's cotton or similar) into the brood chamber.
5. Roof Because we used a 10" wide plank for our lumber, we didn't have a single piece large enough to make a roof that would cover the box and have an overhang to protect the nest from rain. Therefore, we glued together two 10" by 14" pieces (with an extra strength exterior glue) to create a 20" by 14" roof. This size ensured a minimum 1½" overhang on all sides and extra at the front to protect the landing area. We choose a larger size quarter-round (½" by ¼") than strictly needed to make a drip cap so it had extra strength to reinforce the joint. Four lengths of molding are needed to make the drip cap. The ends were mitered to 45° to create close-fitting corners and the pieces were fixed to the underside of the roof, flush with the edges. We also fixed a couple of short, spare pieces of molding across the roof joint near to the center for added strength. Attach the roof to the top of the nest with a couple of screws, or simply weigh it down with a few bricks or rocks (enough to deter raccoons).
An extra component that some people choose to add is an acrylic panel across the top of the nest, so they can lift the roof occasionally and see what is happening inside. Be warned: looking too often can disturb the bees and cause them to abandon the nest, especially in the first few days after the nest is founded.
6. Finishing If you read other guides to making bumble bee nests you will find differing opinions about finishing the box. Some suggest painting the outside of the nest so it will resist the weather but others will say not to, claiming that the paint leaves a toxic odor that might discourage bees and that the box won't be in the weather long enough to justify the extra work. Although there is no way to know how quickly the nest might be occupied-it may have to survive the elements for a few years-we feel that the lumber we used will be able to cope, so choose not to paint it. The important thing is to make the joints and cracks weather tight with caulking or similar, to have a roof that will keep the rain out, and to keep the nest box up off the ground.
Placing your bumble bee nest
Place your nest on bricks or lumber spacers (to keep it up off the damp ground)
with the entrance hole between 4" and 10" off the ground. Choose a
site that is undisturbed (not, for example, somewhere you will be mowing), in
partial or full shade, where there is no risk of flooding, and where it is not
close to a known ant colony. You might like to follow the discoveries of Frison
and be sure there are some obvious landmarks close by.
Put your nesting box out in April, or whenever you first notice bumble bees in the spring or the first willows and other flowers are blooming, and be patient. There is a good chance that no-one will use it. Often, only one in three boxes will be occupied. If it has no inhabitants by late July, put the nesting box into storage until next spring. Try to avoid inspecting your nest too frequently (especially tempting if you have an acrylic inner roof). If a queen gets disturbed before being settled completely, she will move on. Similarly, even when they have established nests, bumble bees are still affected by disturbance and may abscond if they don't like it.
Making a nesting place for bumble bees is a great way to help them. Obviously, bumble bees also need somewhere to feed, so you also should plant flowers to provide them with nectar and pollen from early spring to late summer. But that's more than we can cover here. Check out the pages on the Xerces Society website for information about native plants and garden flowers that are bee-friendly.
(We are happy for you to copy or reproduce this information in anyway you like,
as our aim is to spread information as far and wide as we can. Please just credit
the Xerces Society.)
Other Resources:
Two books worth reading are Humblebee Bumblebee, by Brian Griffin,
and Bees of the World, by Christopher O’Toole and Anthony
Raw. There are also many good sites for bumble bees on the Internet. One of
the best sites for general information is Mrs.
Smith’s bumble bee pages. For information on making bumble bee nests,
try the beetools webpage. Two
sites that will help identify the bees you see are the Key
to the Bombus of Evergreen and the Bee
Biology and Systematics Laboratory of Logan Utah homepage.
©2002, The Xerces
Society
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