Does the Rusty-Patched Bumble Bee Still Haunt Maine’s Landscape?

Bombus affinis USGS

A rusty-patched bumble bee from Sky Meadows, VA in 2014. Photo by the USGS Bee Inventory and Monitoring Lab.

With Halloween just a day away, who wouldn’t love a good ghost story to liven up our favorite spooky holiday?! But this ghost story is a true tale – about a once common species in the midst of a very scary vanishing act. Named for the distinctive orange-brown patch on its abdomen, the Rusty-patched Bumble Bee (Bombus affinis) was once a common sight throughout its range, which extended across the eastern United States from Maine south through Georgia and west to Minnesota and southern Canada. But since the late 1990s, this species has undergone an alarming population crash. Today, its numbers have declined by an estimated 95% and its geographic range has shrunk by 87%. To find a Rusty-patched Bumble Bee anywhere today would be like looking for a ghost!

The specific cause of this decline is unknown, but there are some plausible theories at the front of the line. All bumble bees in the United States face similar threats: widespread use of pesticides; introduced parasites and diseases spread through the use of commercially-raised bumble bees; habitat loss and fragmentation; and in some cases, climate change. The Rusty-patched is not the only bumble bee that is disappearing from the North American landscape. At least three other species have experienced similar rangewide declines, including another Maine native – the Yellow-banded Bumble Bee (Bombus terricola). But not all of the continent’s 46 bumble bee species are in trouble. Some are even expanding their range and increasing in abundance compared to historical data. So why are some species vanishing while others seem to be doing just fine? One explanation may be genetics. Interestingly, three of the four species undergoing severe declines, including the Rusty-patched, are closely related to each other. Perhaps they share the same susceptibilities to threats that other species are more tolerant of?

This past year, the International Union for Conservation of Nature classified the Rusty-patched Bumble Bee as “Critically Endangered” (extremely high risk of extinction in the wild). Just last month, the U.S. Fish & Wildlife Service announced it is initiating a status review to determine if the species qualifies for listing under the federal Endangered Species Act. With the exception of a few isolated populations in the Upper Midwest and southern Ontario, where individuals are rarely observed, this once abundant and widespread pollinator now appears to have vanished from most of its former range. But what about Maine – could it still be here, hiding like a ghost in isolated corners of the state?

The last credible record of a Rusty-patched Bumble Bee in Maine was in 2009. Despite continued searching in the same area, it has not been seen again. But if there is any hope of finding it, it will likely be in the next few years. The Maine Bumble Bee Atlas (MBBA) project, which got underway this past spring, is unleashing a small army of citizen scientists to survey Maine’s bumble bee fauna over the next five years. Maybe we’ll get lucky, like they did in Virginia last year when ONE Rusty-patched Bumble Bee was found amongst 35,000 bees collected during an intensive sampling effort. And there is some good news that could herald a possible discovery of our own hidden population of Rusty-patched Bumble Bees. While still in decline in other parts of its range, the Yellow-banded Bumble Bee appears to be making a comeback in Maine and the Northeast! Last year it was present at nearly half of the field sites sampled by the University of Maine and this year it is turning up in most of the MBBA collections from across the state. If its sister species can develop resilience to and bounce back from the threats that sent them both into rapid decline, and if it’s not too late, the Rusty-patched Bumble Bee might just have a chance for a similar recovery and once again haunt the Maine landscape.


For more information about the Rusty-patched Bumble Bee:

The Xerces Society:

A Ghost In the Making:

COSEWIC Assessment and Status Report:

The IUCN Red List of Threatened Species:


For more information about the Maine Bumble Bee Atlas:

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