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Montana Field Guides

Northern Rocky Mountains Refugium Caddisfly - Goereilla baumanni

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Species of Concern
Native Species

Global Rank: G1
State Rank: S2
(see State Rank Reason below)

Agency Status

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State Rank Reason (see State Rank above)
This NRMR Caddisfly is currently ranked a "S2" Species of Concern in MT and at risk because of very limited and/or potentially declining population numbers, range and/or habitat, making it vulnerable to extirpation in the state. Limited sites with small populations and specialized habitats. This species is a rare, endemic caddisfly only found in specific streams in the Pacific Influenced areas of Montana and Idaho (referred to as the Northern Rocky Mountian Refugium).
  • Details on Status Ranking and Review
    Northern Rocky Mountains Refugium Caddisfly (Goereilla baumanni) Conservation Status Review
    Review Date = 09/18/2008
    Population Size

    ScoreU - Unknown


    Range Extent

    ScoreB - 100-250 km squared (about 40-100 square miles)

    Comment<100-250 square km (less than about 40-100 square miles)

    Area of Occupancy

    Comment40-200 km (25-125 miles) linear river

    Length of Occupancy

    ScoreLC - 40-200 km (about 25-125 miles)

    Long-term Trend

    ScoreD - Moderate Decline (decline of 25-50%)

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

    Short-term Trend

    ScoreE - Stable. Population, range, area occupied, and/or number or condition of occurrences unchanged or remaining within ±10% fluctuation


    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
The larvae of the caddisfly, Goereilla baumanni, occurs in high-gradient, 1st or 2nd order, perennially flowing, forested springs and streams (especially in gravel under mossy areas) of the Rocky Mountain Refugium Area (ID/MT boundary area). The small rock larval case of G. baumanni makes it somewhat distinctive compared to other caddisfly families and only another rare caddisfly, Rossiana (Rossianidae) should be confused with it while sampling in these areas.

Diagnostic Characteristics
Adult morphology: See Denning 1973 for detailed adult description. Larval morphology: See Wiggins 1996 for detailed larval and pupa descriptions. Body length is up to 9 mm for mature larvae. Larvae have single abdominal gills and lack chloride epithelial. Larvae of G. baumanni could be confused only with larvae of Rossiana montana, but their head lacks a flange or carina as in R. montana. G. baumanni larvae also have a slightly extended mesiepisternum into a spiny lobe. Larvae are found in first order streams where they are found in side-channel seepage areas (Wiggins 1996). Larvae construct smooth tubular cases of small rock and some sand grains.

Species Range
Montana Range Range Descriptions


Range Comments
Rangewide, G. baumanni is a regional endemic only known to occur in the Northern Rocky Mountain Refugium area of Montana and Idaho (Wiggins 1996, NatureServe 2006, Stagliano et al. 2007). In Montana, G. baumanni has been reported from two counties, Missoula and Mineral. In Idaho, G. baumanni has been reported from one stream in Clearwater County.

Observations in Montana Natural Heritage Program Database
Number of Observations: 4

(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 is associated with high elevation, forested, perennially flowing cold-spring seep areas (Wiggins 1996) and will be found in slower pooled areas than Rossiana montana (D. Stagliano, personal observation).

Food Habits
Not studied in Montana.

The trophic relationship of larvae of G. baumanni include shredders and collectors-gatherers (eating detritus and plant pieces) (Merritt and Cummins 1996, Wiggins 1996).

Reproductive Characteristics
In Montana, adults of this species emerge from mid-July to mid-August (Wiggins 1996).

Goeriella baumanni has been described as a rare species due to habitat specificity (Wiggins 1996) and is never abundant when collected. It has no USFWS status at the present time, although it is currently a US Forest Service Species of Concern (SOC); ranked globally at high risk/at risk (G1G2) by Natureserve (2011), at risk (S2) in Montana, and unranked (SNR) in Idaho.

Threats or Limiting Factors
Specific threats to Montana and Idaho populations of G. baumanni would include mismanagement of forested riparian areas, including sediment and temperature increases associated with road building and timber harvests not following BMPs. In general, stenothermic (cold-loving) invertebrate populations 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 and aquatic habitat is the primary concern for Idaho and Montana populations.

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Citation for data on this website:
Northern Rocky Mountains Refugium Caddisfly — Goereilla baumanni.  Montana Field Guide.  .  Retrieved on , from