Extension Communications
Extension 4-H Youth Building
Ames, Iowa 50011-3630
(515) 294-9915
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Extension Communications |
12/20/04
Contacts:
Laura Jesse, Entomology, (515) 294-1101, lrahnsen@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,
jmcguire@iastate.edu
Garden column for the week of Dec. 24, 2004
Busy Little Bumble bees
By Laura Jesse
Entomologist
Iowa State University Extension
Wondering why you are reading about bumble bees in winter? Well, as you stare out the window at the cold, gray sky, you might need a reminder that, yes, summer will be back and, once again, we will be surrounded by sunshine and flowers. You also might also wondering, just how all of those bumble bees are planning to survive winter in Iowa.
There are about 50 different species of bumble bees in North America. You can easily identify them by their large, round, fuzzy bodies and their yellow and black coloration. Size and coloration can vary between the different species. Many of the bumble bees we see in Iowa are about half inch long. Bees have wax-producing glands that secrete the wax they use to build their nests. They also have a structure on their hind legs called a pollen basket, which consists of long fringed hairs used to hold pollen.
There is actually a myth that bumble bees cannot fly. It was proposed that bumble bees have wings too small to support their large bodies in flight. It is true that if there was an airplane with wings and body in the same proportions as that of the bumble bee it would never get off the ground. This is because airplanes must hold their wings rigidly in place. The bumble bee however is free to move its wings all around, creating much more lift.
Like wasps and other bee species, bumble bees live in colonies. Each spring the queen chooses a new site at which to establish her colony, preferring to nest underground or in a sheltered area. Common nest sites include old rodent or bird nests, beneath rocks or under leaf litter. They can occasionally be found under the floor of an outdoor building, within a wall cavity or even in a clothes dryer vent.
Once the queen has located a good site, she lines it with dry grass or moss. She then begins gathering enough pollen and nectar to start her nest - a small ball of pollen and wax. Once she has collected enough pollen, she lays a small number of eggs on the pollen ball. When the eggs hatch, the larvae begin feeding on the pollen ball. Eventually, the larvae pupate and adult female worker bees emerge to help the queen maintain and expand her colony. Throughout the summer, the colony continues to grow. The queen lays more eggs and the adult worker bees enlarge the nest and bring back more food for the larval bees. Bumble bee nests remain small with, at most, only a few hundred individuals. By late summer, new reproductive males and females (kings and queens) are produced. They leave the nest and mate with bumble bees from other colonies.
Once fertilized, the new queens move to hibernation sites, such as the shelter of loose bark, hollow trees or other dry, protected places, where they lie dormant through the winter. The males and workers still in the colony die with the first hard freeze. Right now, the only surviving bumble bees are the new, mated queens in hibernation. In the spring the new queens start the process all over again. Unlike honey bees, bumble bees do not remain in the same nest for many years, though they will sometimes build a new nest in the same area.
If you are lucky enough to have a bumble bee nest in your yard, it is best to leave it alone. Bumble bees are not aggressive and the colony does not have enough individuals to be hazardous. However, if a nest is located in a high traffic area and posing a problem, it may be necessary to kill it with insecticides. Moving a bumble bee nest, while possible, can be tricky and protective clothing is definitely a must.
Bumble bees are important pollinators of flowers in your garden. They also are important pollinators of blueberries, tomatoes, eggplants and peppers. They are particularly good pollinators because they are able to fly at colder temperatures than honeybees. Their round, fuzzy bodies hold heat well, and they produce their own body heat by repeatedly moving their wing muscles.
Bumble bees are sometimes used in greenhouses to pollinate crops, particularly tomatoes grown during the winter. Bumble bees are well suited to enclosed situations because they are not aggressive and tend not to fly at windows in order to escape as much as other bee species. So, as you are enjoying that tomato on your salad in the middle of winter, think about the fact that it may have been pollinated by a bumble bee.
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There are no photos for this week's column.
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