uet to identify both rewarding and unrewarding flowers. In addition, bumblebees rely on this chemical bouquet more when the flower has a high handling time (i.e. it takes a longer time for the bee to find the nectar).
Once they have collected nectar and pollen, bumblebees return to the nest and deposit the harvested nectar and pollen into brood cells, or into wax cells for storage. Unlike honey bees, bumblebees only store a few days' worth of food and so are much more vulnerable to food shortages.
Providing Nest Locations for Bumble Bees. Unlike solitary bees, which can be very particular about tunnel diameters, bumble bees are flexible in their nesting needs. All they want is a warm, dry cavity, roughly the size of a shoebox (Figure 44). Artificial nests can be constructed to attract bumble bees, but occupancy is typically extremely low – often far less than 25 percent.
A simple wooden bumble bee box can be made from preservative-free lumber. An appropriate size will have internal dimensions of about 7 inches high by 7 inches wide and 7 inches long. Drill a few ventilation holes on the upper sides of the box (near the roof) and cover with window screen to deter ants. Also drill some drainage holes in the bottom. Make an entrance tunnel from 3/4-inch diameter plastic pipe and fill the box with soft bedding material, such as short lengths of soft unraveled string, dry straw or upholsterer's cotton (do not use cotton balls, as the fibers become tangled in the bees' legs). The box must be weather tight; if the nest gets damp, the larvae may become too cold and mold and fungus will grow.
Bumble Bee Box.
Place the nest in a dry, undisturbed area that has some obvious landmarks (a fence post, rock or building) to aid bee navigation; these landmarks are important to bees returning from foraging. Nesting boxes that are at ground level or slightly buried (either with soil or straw) are the most attractive to queens of many species. Boxes placed on the surface should be level and stable. If you are burying your box, extend the entrance pipe so it gently slopes up to the surface and clear the vegetation from an area a few inches around where the pipe surfaces.
The best time to install a bumble bee nest box is in early spring, when the first queens have emerged from hibernation and are searching for a nest site; in many areas, this is when the willows first start blooming.
Bumble bee nests require little maintenance. Watch your boxes through the spring and early summer. Any above-ground boxes that are unoccupied by late July can be removed, cleaned and put into storage until the following spring. This is not vital, and if you have a lot of boxes on a large site it may not be practical. In late fall or early winter inspect all the boxes that have been occupied. Remove the old nests, clean them and make any repairs. Cleaning the boxes with a bleach-water solution (1:2 ratios) will help reduce parasites and diseases in the nests. The following spring, add fresh nesting material to all the boxes.
The package bumble bee industry, which provides farmers with live bumble bee colonies for crop pollination, currently only produces a single eastern bumble bee species, Bombs impatiens. This species is then shipped nationwide, in a situation similar to the blue orchard bee, often far beyond its native range. Many bumble bee scientists now believe that these commercially produced bumble bees are responsible for the introduction of one or more diseases which have decimated several bumble bee species, even causing the potential extinction of one species, Bombus franklini (Franklin's bumble bee).
There is an enormous need for managed agricultural pollinators in this country, but it critical not to import non-local bees, especially near wild areas, even if the bees are represented as being the same species as local bees. The alternatives are to either develop local commercial sources of bees that are native to your region or to rear already widely established non-native species, such as honey bees or the alfalfa leafcutter bee, as managed pollinator