Endangered Species
Mountain-Prairie Region
ARAPAHOE SNOWFLY

Arapahoe snowfly

The Arapahoe snowfly 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. Therefore, their presence can be an indication of a healthy stream ecosystem.

The Arapahoe snowfly is a small, dark colored insect with both a body length and wing length of approximately 0.2 inches. It has only been found in two small tributaries (Elkhorn Creek and Young Gulch) of the Cache la Poudre River in the Front Range of the Rocky Mountains of Colorado. Both sites are on USDA Forest Service lands. The species has not been found in Young Gulch since 1986, and may no longer occur at this site.

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.

Recent Actions: 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.

Last updated: May 11, 2012