Building Bumble Bee Nests

Here is a simple set of plans for building your own Bombus nests as a winter project. I've always wanted to try this and I’ve had several people ask about bumble bee nests and keeping other bees as pollinators, so I searched around and found a couple of different plans for the nests.

General Information

Bumble bees are very efficient pollinators. They work flowers that have no nectar, unlike honeybees. They also grab the anthers of flowers and shake them, which is necessary to free pollen in some blossoms. Bumble bees will work on cool overcast days while honeybees remain in their hives.

The accompanying drawings illustrate some of the basic needs of the bumblebees for an outside nest but are suggestions only (nests in greenhouses are slightly different as they are out of the weather and the bees are captive in the greenhouse). An "ultimate" nest will only come about by trial and error and careful observations by interested individuals. A supply of dry insulation material in a dark undisturbed area is the bee’s basic requirement. Also desirable is limited access - for defence purposes.

Two chambers are also helpful. This provides them with a vestibule area where they can defecate rather than contaminating their nest area. Other features that add to the attractiveness are a tunnel entrance, protection from the weather, ventilation and colour contrast at the entrance. Several studies seem to indicate that a pattern or 'marker" of some type at the entrance helps the bees with orientation and location of the nest. A couple of colours they seem to like are pale yellow and mauve. But again, only time and experimentation will reveal the ultimate solutions.

Last but not least is hygiene. Nest boxes must be sterilised and contaminated items disposed of each year. Consequently it is suggested that you DO NOT USE PLYWOOD except for tops which are not in contact with the bees, unless you plan to replace it each year. It has been found that plywood cannot normally be properly sterilised.

The drawings show upholsters cotton which is readily available at upholsters shops and is relatively inexpensive. Nevertheless, several people have observed that the bees seem to be quite happy with fibreglass insulation (in the walls of sheds). This is an area that needs more field trial and observation. It could be that different bumblebees prefer different nesting material.

Nest

Nests must be dry and well insulated because bumblebee larvae are very sensitive to temperature extremes. If they temperature drops below 30"C (the bees create their own heat) the young's growth will be stunted.

As with any collection of bees, cleanliness is very important. This is particularly true with bumble bees as they will defecate in their nest area. Therefore, the nest should have two chambers, a vestibule chamber where the bees can defecate and a nesting chamber, which should be about 6" x 6" or slightly larger, The vestibule can be slightly smaller.

A landing surface at the entrance is an attraction, particularly for inexperienced foragers. The use of a tunnel entrance with no steps allows the colony to better protect itself. The ideal entrance diameter is 5/8th of an inch but no larger than 3/4 of an inch. The inside divider needs to be rough so bees can get a grip when they climb over it. Make sure adequate weather protection is provided (i.e. overhanging roof). Paint around the entrance hole to provide colour contrast; an "orientation-pattern" seems to be even more attractive.

Tips

Let your nest box weather outside for a while before you put it into use. This will allow any paint or caulking odours to disappear. Set out the nest in early spring when the first flowers such as willows are starting to bloom. Bumblebees may search all day long for up to two weeks to find an "ideal" nest site. If you are planning to introduce a queen, rather than take a chance that one will find it, it has been suggested that you get a bee without pollen in her baskets. The theory is that if she is carrying pollen then she has already chosen a nest site and consequently will not stay in yours. This theory may be true but still needs some research.

Notch the plastic pipe to accept the 4 x 2s. Drill 5/8 inch hole from one end

of the 4 x 2 at an angle to form the entrance. In the centre of the 4 x 2 drill a 1inch hole to provide connection between the chambers. Drill vent holes in the plastic pipe (to provide ventilation at both ends of the nest.) Cover the holes with fine mesh. Assemble the pipe sections and the 4 x 2 on the base plate using silicone sealant. Place a cut-to-fit piece of corrugated cardboard on the vestibule floor (this will allow for easy clean up) Place a plywood cover on top. Weigh down the top with a brick or stone so it will not blow off in a wind.

From GWENYN KERNOW – the newsletter of the Cornwall Beekeepers Association. Via BEES.

Bumblebees are very fickle. They may use your nest one-year but not the next. Also, if they find a better location before they are settled or if they are too badly disturbed, they will move. If you get one box in three occupied, consider yourself lucky. DO NOT take off the nest cover (once nesting has started) more than once a day or the bees will probably vacate.