Office of External Affairs
Mountain-Prairie Region


U.S. Fish and Wildlife Service
Mountain-Prairie Region
134 Union Boulevard
Lakewood, Colorado 80228

April 25, 2011

Contacts:  Susan Linner  303-236-4773

                  Joy Gober  970-226-9195




Public Comment Period Closes on June 27, 2011


The U.S. Fish and Wildlife Service announced today that the Arapahoe snowfly, an insect found in two tributaries of the Cache la Poudre River in Colorado, may warrant Federal protection as an endangered or threatened species under the Endangered Species Act (ESA).  We will undertake a more thorough review of the Arapahoe snowfly to determine whether to propose adding the species to the Federal list of threatened and endangered wildlife and plants.


The Arapahoe stonefly is a species of insect in the order Plecoptera (stonefly).  Stoneflies, including the Arapahoe snowfly, are typically found in cold, clean, well-oxygenated streams and rivers.  They are sensitive to most types of pollution.


The Service’s decision, commonly known as a 90-day finding, is based on scientific information about the species provided in a petition from WildEarth Guardians and others requesting listing of the species under the ESA.  The finding on the petition does not mean that the Service has decided it is appropriate to list the Arapahoe snowfly.  Rather, this finding is the first step in a long process that triggers a more thorough review of all the biological information available. 


To ensure this status review is comprehensive, we are soliciting information from State and Federal natural resource agencies and all interested parties regarding the Arapahoe snowfly and its habitat.


Based on the status review, we will make one of three possible determinations:


  • Listing is not warranted, in which case no further action will be taken.
  • Listing as threatened or endangered is warranted.  In this case, we will publish a proposal to list, solicit independent scientific peer review of the proposal, seek input from the public, and consider the input before a final decision about listing the species is made.  Generally, there is a 1-year period between the time a species is proposed and the final decision.
  • Listing is warranted but precluded by other, higher priority activities.  This means that the species is added to the Federal list of candidate species, and the proposal to list is deferred while the Service works on listing proposals for other species that are at greater risk.  A

warranted but precluded finding requires subsequent annual reviews of the finding until such time as either a listing proposal is published, or a not warranted finding is made based on new information.


The Arapahoe snowfly was first discovered in 1986 in Young Gulch, a small tributary of the Cache la Poudre River in the Front Range of the Rocky Mountains of Colorado.  It is a small, dark-colored insect with both a body length and wing length of approximately 0.2 inch.  In 1988, it was identified as a new species of insect in the order Plecoptera (stonefly).  It was also found in a second tributary, Elkhorn Creek, approximately 5 miles from Young Gulch.  No other populations have been found in searches of nearby tributaries, and numerous visits to Young Gulch since the species’ discovery in 1986 have failed to locate additional specimens.  The species is currently only known to occur in Elkhorn Creek.  The species has a complex 1-year lifecycle that requires terrestrial habitat during its adult phase and aquatic habitat during immature phases.  In late winter, adults emerge from beneath stream ice to mate.  Females detach an egg mass onto the water and eggs hatch in early spring.  As water temperatures rise, nymphs move into the stream substrate and undergo a period of inactivity during the warm months.  As water temperatures drop in the late fall, nymphs complete their development into adults.


Scientific information will be accepted until June 27, 2011. Anyone wishing to submit information regarding the Arapahoe snowfly may do so by writing to Public Comments Processing, Attn: FWS-R6-ES-2011-0019; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, Suite 222; Arlington, VA 22203 or by electronic mail to  In the box that reads “Enter Keyword or ID,” enter the docket number for this finding.  Check the box that reads “Open for Comment/Submission,” and click the Search button.


For more information about the Arapahoe snowfly and this finding, please visit the Service’s website at


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