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Mountain-Prairie Region
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Western glacier stonefly


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  • Western glacier stonefly. Credit: USFWS.

    Western glacier stonefly. Credit: USFWS.

Western glacier stonefly (Zapada glacier)

The western glacier stonefly (Zapada glacier) is a species of insect in the taxonomic order Plecoptera, also known as the stonefly order.  Immature western glacier stoneflies (nymphs) are aquatic and emerge from streams at specific times to complete their development into adults.  Western glacier stonefly adults are generally brown in color, possess two sets of translucent wings and are very small; ranging from 0.26 to 0.39 inches in body length. 

Western glacier stoneflies are known to occur in 16 streams; 6 in Glacier National Park, Montana, 4 in Grand Teton National Park, Wyoming and 6 in the Absaroka/Beartooth Wilderness, Montana.  All occupied streams are high-elevation, alpine streams originating from cold water sources, including glaciers and small icefields, permanent and seasonal snowpack, alpine springs, and glacial lake outlets.  Recent collections of the western glacier stonefly were in habitats with daily maximum water temperatures less than 6.3°C (43°F). 

Western glacier stoneflies occupy the most upstream reaches of alpine streams, typically occurring within the first one half mile of stream, starting at the meltwater source.  Therefore, they are sensitive to temperature changes and are considered to be a barometer for the effects of climate change in the alpine environment. 

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October 31, 2017: The U.S. Fish and Wildlife Service has reopened the comment period for an October 4, 2016, proposed rule to list the western glacier stonefly and the meltwater lednian stonefly as threatened species under the Endangered Species Act.  The comment period is being reopened to accept additional comments on new information about the range of the species.

October 3, 2016: The U.S. Fish and Wildlife Service is proposing a rule to list the meltwater lednian stonefly and western glacier stonefly as threatened under the Endangered Species Act. A threatened listing means the stoneflies are likely to become in danger of extinction in the foreseeable future.  The public is invited to comment on this proposal until December 5, 2016.

The Service completed a 90-day finding on a petition to list the western glacier stonefly under the Endangered Species Act (ESA).  After evaluating all of the scientific information described or cited in the petition and information readily available in our files, we concluded that the petitioners provided substantial information indicating that protecting the species under the ESA may be warranted.  Therefore, we are initiating a full biological status review to determine if listing the species is warranted.


The mission of the U.S. Fish and Wildlife Service is working with Others to conserve, protect, and enhance fish, wildlife, plants and their habitats for the continuing benefit of the American People.
Last modified: November 03, 2017
All Images Credit to and Courtesy of the U.S. Fish and Wildlife Service Unless Specified Otherwise.
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