Center for Biological Diversity

For Immediate Release, April 27, 2021


Jess Tyler, (406) 366-4872,

Endangered Species Act Protection Sought for Variable Cuckoo Bumblebee

Pollinator Devastated by Pesticides, Loss of Host Species, Habitat

WASHINGTON— The Center for Biological Diversity petitioned the U.S. Fish and Wildlife Service today to grant Endangered Species Act protection to the critically endangered variable cuckoo bumblebee.

This foraging generalist, capable of pollinating a wide variety of plants, was once found in 28 states, mainly in the East. But it has not been seen since 1999.

The decline of the variable cuckoo is tied to pesticide use, habitat destruction and the decline of its host species, the American bumblebee, which is also gravely imperiled.

“This amazing cuckoo bumblebee could not need protection any more urgently,” said Jess Tyler, an entomologist and staff scientist at the Center. “It’s in a great danger of disappearing forever. With this petition we’re sounding the alarm, and we hope the Biden administration will step up to save this important pollinator.”

This distinctive bee is unusual — a social parasite or “cuckoo” species that takes over the nests of other bumblebees by subduing the resident queen and making the worker bees feed and care for its own young. In doing so, cuckoo bumblebees help keep host bumblebee populations diverse and healthy, including by reducing disease virulence.

The variable cuckoo bumblebee relies entirely on the success of its host species, the declining American bumblebee. The Center petitioned earlier this year for Endangered Species Act protection for the American bumblebee, which was once among the country’s most commonly observed bumblebees but has declined by an estimated 89%.

“Insects like this are quietly disappearing, and without them our world is a lonelier, less healthy and less interesting place,” said Tyler. “We need to take urgent action to turn around the heartbreaking extinction crisis, and listing this amazing bumblebee is an important step toward protecting pollinator biodiversity.”

Cuckoo bumblebees’ reliance on host species makes them especially vulnerable. Multiple, concurrent threats also degrade the variable cuckoo bumblebee’s health and habitat. Habitat loss and degradation limit the available nutrition from diverse pollen and nectar sources and weaken bumblebee immune systems. Pesticide use reduces survival and harms reproduction as well as immune systems. Weakened immune systems make the bees more susceptible to diseases that are spread by domesticated bumblebees and honeybees.

The variable cuckoo bumblebee can survive in a wide range of open habitats, including urban areas. They make their nests in pre-existing cavities like rodent burrows and rotten logs, or on the surface of the ground in large grass bunches.

The cuckoo was once common in states like Illinois, Kansas and Florida where it could be found in open grasslands and meadows. Although it was found mainly in the eastern United States, it was observed as far southwest as Arizona and as far northeast as New Hampshire.

It was last seen in Nebraska, Missouri and Florida.

Variable cuckoo bumblebee/USGS Image is available for media use.

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.7 million members and online activists dedicated to the protection of endangered species and wild places.

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