Western Glacier Stonefly - Zapada glacier
State Rank Reason (see State Rank above)
The Western Glacier stonefly is currently ranked "S1" in Montana because it is thought to be at high risk due to very limited and/or potentially declining population numbers, range and/or habitat, making it extremely vulnerable to extirpation in the state. This species is particularly vulnerable due to it's very restricted habitat and cold water temperature requirements.
The Western Glacier Forestfly is a small, dark colored stonefly reported only within the habitats of glacial-fed streams in Glacier National Park. This species is one of 7 species of globally-rare insects within Glacier National Park that will be adversely affected when the glaciers have completely melted.
In Montana, the adults have been collected in July (Baumann et al. 1977), and the larvae probably require at least 1 year to develop.
Larvae have not been associated with the adults or distinguished from other Z. oregonensis group species, although they share the typical characters of the group: cervical gills simple, unbranched and not constricted past the base (see photo of full view larva). Thus, this species would not be identified to species and left within this species group level by taxonomy labs identifying bioassesment samples. Adults described in Baumann and Gaufin (1971) (see photo of adult).
Rangewide, Zapada glacier is known only from Glacier National Park, Montana, but may also occur in Waterton Park, Alberta, but is difficult to collect (glacier-fed streams) at high elevations early in the year. Only about five occurrences are known. In Montana, Z. glacier has been reported from scattered localities in Glacier Park, including Cataract Creek, Iceburg, Grinnell, Ptarmigan and Wilbur Creeks below glaciers or glacial lakes (Baumann and Gaufin 1971).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
This species occurs in steep (precipitous) glacial-influenced streams (Baumann et al. 1977).
The morphology of the mouthparts suggests that Zapada glacier is well-suited for shredding plant materials, thus trophic relationships would include being shredders and collectors-gatherers (detritus, CPOM) (Merritt and Cummins 1996).
In Montana, the adults have been collected in July (Baumann et al. 1977).
On October 4, 2016 the U.S. Fish and Wildlife Service proposed listing the Western Glacier Stonefly under the Endangered Species Act due to primary threats to the habitat and range of this species including climate change, loss of glaciers and permanent snowfields, and changes in stream flow and water temperature. On November 21, 2019 a notice was published in the Federal Register that the species' status was determined to be Threatened. Further information on status can be found on the U.S. Fish and Wildlife Service's Species Account
Threats or Limiting Factors
With the increased evidence of global warming and melting glaicers in GNP, this species could be considered a candidate for the USFWS Threatened and Endangered species list.
- Literature Cited AboveLegend: View Online Publication
- Baumann R.W. and A.R. Gaufin .1971. New species of Nemoura from Western North America. Pan-Pacific Entomologist 47(4):27.
- Baumann, R.W, A.R. Gaufin, and R.F. Surdick. 1977. The stoneflies (Plecoptera) of the Rocky Mountains. American Entomological Society, Philadelphia.
- Merritt, R.W. and K.W. Cummins. 1996. An introduction to the aquatic insects of North America. 3rd Edition. Kendall/Hunt Publishing Company. Dubuque, Iowa. 862 pp.
- Additional ReferencesLegend: View Online Publication
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- Giersch, J.J., S. Jordan, G. Luikart, L.A. Jones, F.R. Hauer and C.C. Muhlfeld. 2015. Climate-induced range contraction of a rare alpine aquatic invertebrate. Freshwater Science. 34 (1).
- Muhlfeld, C.C., T.J. Cline, J.J. Giersch, E. Peitzsch, C. Florentine, D. Jacobsen, and S. Hotaling. 2020. Specialized meltwater biodiversity persists despite widespread deglaciation. Proceedings of the National Academy of Sciences May 2020, 202001697; DOI: 10.1073/pnas.2001697117
- Newell, R.L. and R.W. Baumann. 2013. Studies on distribution and diversity of nearshore Ephemeroptera and Plecoptera in selected lakes of Glacier National Park, Montana. Western North American Naturalist 73(2): 230-236.
- Additional Sources of Information Related to "Insects"