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Mountain-Prairie Region
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Arapahoe snowfly

 

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Update - August 2019:

The U.S. Fish and Wildlife Service determined that Endangered Species Act protection is not necessary for the Arapahoe snowfly because it is not a valid species or subspecies and is therefore not a listable entity under the Endangered Species Act. This decision is based on a comprehensive review of the best available scientific and commercial information, in addition to relevant laws, regulations, and policies. A recent genetics study has shown that the Arapahoe snowfly is a hybrid between two other species. Instead of representing a distinct taxon, individuals formerly recognized as the Arapahoe snowfly should be referred to as first-generation hybrids between female Arsapnia decepta and male Capnia gracilaria that appear in the narrow zone of range overlap between the parental species in northern Colorado. Because we no longer recognize the Arapahoe snowfly to be a valid species or subspecies, it is not a listable entity under the Endangered Species Act.


  • Arapahoe snowfly Credit: USFWS.

    Arapahoe snowfly Credit: USFWS.


Arapahoe Snowfly (Arsapnia arapahoe)

The Arapahoe snowfly was believed to be a species of insect in the order Plecoptera (stonefly). Stoneflies are typically found in cold, clean, well-oxygenated streams and rivers. They are sensitive to most types of pollution. Therefore, their presence can be an indication of a healthy stream ecosystem.

A recent genetics study has shown that the Arapahoe snowfly is a hybrid between two other species. Instead of representing a distinct taxon, individuals formerly recognized as the Arapahoe snowfly should be referred to as first-generation hybrids between female Arsapnia decepta and male Capnia gracilaria that appear in the narrow zone of range overlap between the parental species in northern Colorado.

This snowfly hybrid is a small, dark colored insect with both a body length and wing length of approximately 0.2 inches. The hybrid insect formerly known as the Arapahoe snowfly occurs on U.S. Department of Agriculture Forest Service, Boulder County Open Space, and private lands in the Front Range of the Rocky Mountains, Colorado.

The insect formerly recognized as the Arapahoe snowfly has a 1-year lifecycle that requires aquatic habitat while it is a nymph and terrestrial habitat as an adult. In late winter, adults emerge from beneath stream ice, fly upstream, and mate. Females detach an egg mass onto the water. The eggs hatch in early spring. As water temperatures rise, the nymphs burrow into the stream substrate and undergo a period of dormancy. When water temperature drops in late fall, the nymphs complete their development into adults.


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Update - August 2019: The U.S. Fish and Wildlife Service determined that Endangered Species Act protection is not necessary for the Arapahoe snowfly because it is not a valid species or subspecies and is therefore not a listable entity under the Endangered Species Act. This decision is based on a comprehensive review of the best available scientific and commercial information, in addition to relevant laws, regulations, and policies. A recent genetics study has shown that the Arapahoe snowfly is a hybrid between two other species. Instead of representing a distinct taxon, individuals formerly recognized as the Arapahoe snowfly should be referred to as first-generation hybrids between female Arsapnia decepta and male Capnia gracilaria that appear in the narrow zone of range overlap between the parental species in northern Colorado. Because we no longer recognize the Arapahoe snowfly to be a valid species or subspecies, it is not a listable entity under the Endangered Species Act.


The U.S. Fish and Wildlife Service found that the Arapahoe snowfly, an insect found in two tributaries of the Cache la Poudre River in Colorado, warrants protection under the Endangered Species Act, but that proposing the species for protection is precluded by the need to address other higher priority species. The species will be added to the list of candidate species and its status will be reviewed annually.


After a review of a petition seeking to protect the Arapahoe snowfly under the Endangered Species Act, we have determined that the species might warrant federal protection as a threatened or endangered species. We will undertake a more thorough status review of the species to determine whether to propose adding the species to the federal list of threatened and endangered species.

To ensure this review is comprehensive, we are soliciting information from state and federal resource agencies and all interested parties regarding the Arapahoe snowfly and its habitat. Scientific information will be accepted until June 27, 2011.

 

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: August 15, 2019
All Images Credit to and Courtesy of the U.S. Fish and Wildlife Service Unless Specified Otherwise.
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