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Montana Field Guide

Montana Field Guides

Northern Rocky Mountains Refugium Stonefly - Soyedina potteri

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Species of Concern
Native Species

Global Rank: G2
State Rank: S2
(see State Rank Reason below)

Agency Status

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State Rank Reason (see State Rank above)
The NRMR stonefly is currently ranked "S2" in Montana because it is thought to be at risk due to very limited and/or potentially declining population numbers, range and/or habitat, making it vulnerable to extirpation in the state. This species is globally restricted to Montana and Idaho.
  • Details on Status Ranking and Review
    Northern Rocky Mountains Refugium Stonefly (Soyedina potteri) Conservation Status Review
    Review Date = 09/18/2008
    Population Size

    ScoreU - Unknown


    Range Extent

    ScoreD - 1,000-5,000 km squared (about 400-2,000 square miles)

    Comment200-1000 km (125-620 miles) linear river

    Area of Occupancy

    Comment200-1000 km (125-620 miles) linear river

    Length of Occupancy

    ScoreLD - 200-1,000 km (about 125-620 miles)

    Long-term Trend

    ScoreE - Relatively Stable (±25% change)

    CommentSiltation and stream temperature increases with loss of riparian shading and lower snowpack probably contributed to some decline

    Short-term Trend

    ScoreD - Declining. Decline of 10-30% in population, range, area occupied, and/or number or condition of occurrences


    ScoreF - Widespread, low-severity threat. Threat is of low severity but affects (or would affect) most or a significant portion of the population or area.

    CommentClimate Change, increasing stream temperatures and lower snowpack could seriously impact the habitat that this speces exists in

    SeverityLow - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.

    ScopeModerate - 20-60% of total population or area affected

    ImmediacyLow - Threat is likely to be operational within 5-20 years.

    CommentThreat is not fully operational now, but some areas have been lost.

    Intrinsic Vulnerability

    ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).

    Environmental Specificity

    ScoreB - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.

    CommentCold water stenotherm, cannot survive increases in water temperatures or will have to migrart to cooler temps

General Description
This is a small stonefly and the general color of the nymphs is light brown/tan; head is light brown and slightly patterned. No cervical gills and the pronotum is rounded at the corners with a definite notch on the lateral margins. This species has generally been collected in small forested streams that are either fishless or contain westslope cutthroat trout.

Diagnostic Characteristics
Adults are macropterous and distinguished by the fusion of veins A1 and A2 in the forewing near the wing margin. Wings are hyaline; anal area of each hindwing is large. Body length is 5.5-7 mm, forewing length is 5-6.5 mm. General color is dark brown; legs are yellowish brown. Cerci are small and membranous. Gills are absent. See Baumann and Gaufin (1971) for more details. Larval body length is 4 mm and caudal filaments are 3 mm. General color is light brown; head is light brown and slightly patterned. No cervical gills and the pronotum is rounded at the corners with a definite notch on the lateral margins.

Species Range
Montana Range Range Descriptions


Range Comments
Rangewide, Soyedina potteri is a Northern Rocky Mountain regional endemic known to occur in Montana and Idaho (Baumann et al. 1977, NatureServe 2015). In Idaho, S. potteri is known from one location in Clearwater County and four locations in Idaho County in the central mountainous part of the state (Baumann et al. 1977). In Montana, S. potteri has been reported from scattered localities in Flathead and Glacier Counties (Baumann et al. 1977), although they don’t mention specific locations, and from four sites in the Northern Rocky Mountain Refugium area of Mineral and Missoula Counties in west-central Montana (Stagliano et al. 2007).

Observations in Montana Natural Heritage Program Database
Number of Observations: 17

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



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

Larval drift and adult movements not studied in Montana.

This species occurs in creeks, small streams, and small springs (Baumann et al. 1977; NatureServe 2015). Merritt and Cummins (1996) describe the habitat associated with members of the genus Soyedina as “spring outflows.” The morphology of the mouthparts suggests that Soyedina is well-suited for biting or shredding, thus its trophic relationships would include shredders and collectors-gatherers (detritus, algae) (Merritt and Cummins 1996).
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Food Habits
Merritt and Cummins (1996) report that members of this family are trophically shredder-detritivores; eating large particulate organic materials such as detritus, leaves and plants.

Due to the habitat and landscape position of the collection sites, this species is likely a cold-water stenotherm, not able to tolerate summer water temperatures much over 10 degrees C.

Reproductive Characteristics
In Montana, the adults emerge from April to July (Baumann et al. 1977).

Soyedina potteri has no USFWS status at the present time, although it is currently a US Forest Service Species of Concern (SOC); ranked globally at risk (G2) by NatureServe (2015), listed as imperiled in Idaho (S1) and at risk (S2) in Montana. These rankings are largely due to habitat specificity and the lack of occurrences.

Threats or Limiting Factors
Specific threats to USFS populations of Soydinia potteri have not been identified. Although, stonefly populations in general are affected by changes to aquatic habitat, such as alteration of flow patterns, streambed substrate, thermal characteristics, and water quality. Alteration and degradation of riparian/aquatic habitat is the primary concern for Northern Region 1 Forest Service populations.

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Citation for data on this website:
Northern Rocky Mountains Refugium Stonefly — Soyedina potteri.  Montana Field Guide.  .  Retrieved on , from