The Xerces Society has put a call out for entomologists and naturalists to help document the host ranges–and declines–of several native bumblebee species:

“In the late 1990’s, bee taxonomists started to notice a decline in the abundance and distribution of several bumble bee species. Three of these species (Western Bumble Bee, Rusty-patched Bumble Bee, and Yellow-banded Bumble Bee) were once very common and important crop pollinators over their ranges. Franklin’s Bumble Bee was historically found only in a small area in southern Oregon and northern California, and it may now be extinct.

The dramatic decline in wild populations of these species occurred about the time that a disease outbreak was reported in populations of commercially raised Western Bumble Bees, which were distributed for greenhouse pollination in western North America. The timing of this suggests that an escaped exotic disease organism may be the cause of this widespread loss.

To better understand what has happened, the Xerces Society is documenting the former and current ranges of these species. This detailed information on past and present distribution and current search efforts will help determine the best methods for protecting those remaining populations. If you have any information on the distribution of any of these four species of bumble bees, please contact us.”

Oddly enough, the American bee species reared commercially were in a European hatchery–and then colonies were sold back into the US. Several entomologists said at the time this was a very bad idea, and it turns out they were correct. The American species seem to have picked up a microsporidian parasite from a European species being reared in the same facility.

This parasite is now a prime suspect in bumble declines, although habitat loss is a major issue as well.

Visit Xerces to learn more about the threats to native bees, and consider helping in this worthy effort. The Rusty-patched bumble bee once occurred in Michigan, but now may be extinct.

[CC image, courtesy Giles ]

Posted by Gwen Pearson

Writer. Nerd. Insect Evangelist. Have you heard the good news? BUGS!


  1. Looks like we both got wind of this situation. It’s alarming that something as common and widespread as the western bumble bee can disappear almost overnight. We caught this in action because we pay attention to bumble bees (they’re charismatic, economically important, conspicuous, etc.), but what is happening to all the other insects out there? Who’s watching the tiphiid wasps? the slime-mold beetles? the crane flies? Scary!
    p.s. love your blog

  2. That’s interesting. The story I’ve heard (from Mace @ Xerces and others in the PNW) is that B. occidentalis was infected with Nosema at a Michigan rearing facility that was growing Bombus colonies for greenhouses.

    Europe, you say? Maybe the Nosema vector, but not the facility.

  3. Thanks for the update. I added their planting fact sheets to my blog. :)

  4. Interesting DB–I’ll see if I can find more info on the source of the colonies.

  5. It would be great if you could, because no one here in the PNW will name names. I think B. occidentalis numbers are stable in other areas, British Columbia for example, and eastern-most PNW states, but it’s all but extinct in the valley and coastal areas.

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