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United States Department of Agriculture

Agricultural Research Service

Bumble Bees (Bombus)
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Bumble bees (Bombus) are important pollinators of crops and native plants.  In North America there are approximately 50 species of bumble bees that inhabit nearly every terrestrial ecosystem on the continent.  Bumble bees are social and single queens form colonies in the Spring that grow throughout the year until the colony matures in the Autumn (Figure 1).  Colonies of some species can reach over 1000 individual bees living and working together.  The colony dies in the Fall of the year when newly emerged queens and males leave the colony in search of mates and overwintering sites.


Figure 1

Bombus come in a variety of colors and sizes.  Many species look similar due to mimicry complexes that form in geographic regions; but usually the bees are fuzzy and have some combination of black, yellow, orange, white, or red bands on their thorax and abdomen (Figures 2-5).  Bombus seen early in the Spring are typically large queens searching for nesting sites, whereas some species produce workers that are smaller than a honey bee.

Figure 2 Figure 3

Figure 4 Figure 5

Bombus research at PIRU is concentrated in two areas:

  1. Developing species that are distributed in the Western U.S. for commercial pollination
  2. Conserving wild bumble bee populations

We raise nests of bombus in the laboratory (Figures 6-7) to test the potential for different species to use in greenhouses (primarily as tomato pollinators - Figure 8).

Figure 6 Figure 7

 
Figure 8

Our conservation work focuses mainly on Bombus occidentalis, the Western Bumble Bee, which was historically widespread, but is now found only in a portion of its historic range.  We are currently documenting the extent of the species range contraction and investigating potential causes of the declines.  See our postcard.


(Download Postcard in PDF format)

Photo Credits:  Lee Solter, Leah Lewis, James P. Strange, Mike Juhl


Last Modified: 4/20/2009