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Montana Field Guide

Montana Field Guides

Western Glacier Stonefly - Zapada glacier

Species of Concern

Global Rank: G1
State Rank: S1
* (see State Rank Reason below)

Agency Status
USFWS: P
USFS:
BLM:


 

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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.
 
General Description
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.

Phenology
In Montana, the adults have been collected in July (Baumann et al. 1977), and the larvae probably require at least 1 year to develop.

Diagnostic Characteristics
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).

Species Range
Montana Range

Click the legend blocks above to view individual ranges.
 


Range Comments
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).

Summary of Observations Submitted for Montana
Number of Observations: 22

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
This species occurs in steep (precipitous) glacial-influenced streams (Baumann et al. 1977).

Food Habits
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).

Reproductive Characteristics
In Montana, the adults have been collected in July (Baumann et al. 1977).

Management
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. Further information on this proposed listing can be found on the U.S. Fish and Wildlife Service’s Western Glacier Stonefly species profile.”>

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.

References
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Citation for data on this website:
Western Glacier Stonefly — Zapada glacier.  Montana Field Guide.  .  Retrieved on , from