The U.S. Fish and Wildlife Service on Wednesday proposed listing the rusty patched bumble bee, a prized but vanishing pollinator once widely found in the upper Midwest and Northeastern United States, for federal protection as an endangered species.

One of several wild bee species seen declining over the past two decades, the rusty patched bumble bee is the first in the continental United States formally proposed for listing under the U.S. Endangered Species Act.

Named for the conspicuous reddish blotch on its abdomen, the rusty patched bumble bee — or Bombus affinis, as it is known to scientists — has plunged in abundance and distribution by more than 90 percent since the late 1990s, according to the Fish and Wildlife Service.