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Montana Field Guides

Meltwater Lednian Stonefly - Lednia tumana

Species of Concern
Native Species

Global Rank: G1G2
State Rank: S1
(see State Rank Reason below)

Agency Status

External Links

State Rank Reason (see State Rank above)
This stonefly is currently listed as an "S1" Species of Concern in MT due to extremely limited and/or rapidly declining population numbers, range and/or habitat, making it highly vulnerable to extirpation in the state or even global extinction. Currently only known from a few locations in Glacier National Park, mostly from larval collections. Currently at risk of becoming extinct due to the melting of the glaciers in Glacier National Park, which it depends on for it's alpine snow-melt stream habitat. It was listed as a "candidate species" for listing under the Endangered Species Act in 2011.
General Description
The Meltwater Lednian Stonefly is a small, dark species of extremely cold glacier-fed streams at high elevations in Glacier Park south through the Mission and Swan Ranges of Northwestern Montana. Little else is known about its habits or ecology, except that the adults have hatched by mid-summer (July-August) and are presumably mating during this time.

[From Baumann and Stewart 1980, Baumann and Kondratieff 2010] Male: Macropterous, wings hyaline with darker veins near cord; length of body 4.5-5.5 mm, dark brown, anterior abdominal segments lightly sclerotized. Female: body color and wings similar to male; length of body 5.5-7.0 mm. Male epiproct bilaterally symmetrical with dorsal groove extending from tip to near base, ventral sclerite flat and dark (bearling few stout ventral spines apically), apex narrowly pointed and extending beyond apex of dorsal sclerite, tip with dorsal groove terminating in arrowhead-like point; dorsal sclerite with borad bare base; hypoproct sclerotized, broad at base and narrowing towards apex; paraprocts with two lobes (dark inner one long and thin, light outer one short and broadly rounded with numerous hairs); tergum ten with median anterior groove bordered by pair of mace-like prongs which approach tip of epiproct. Female sternum seven broadly rounded, subgenital plate covering most of sternum eight, lateral margins bearing nearly rounded sclerotized lobes on either side of subgenital plate apex. Larva: gills absent, length of mature males 4.5-5.5 mm, mature females 5.5-6.5 mm. Dorsal surface of body with few small spines except at anterior margins of thoracic and anterior abdominal segments. Legs with numerous small spines, 3-5 larger spines present on dorsal margins of femora. Female larvae with large, truncate, plate-like lobe on dorsomedian margin of sternum eight. Cerci with whorls of spines on posterior margins of segments and sparse, small intercalary spinules on all segments.

Adults have hatched by mid-summer (July-August) and are presumably mating during this time.

Diagnostic Characteristics
Dorsal sclerite of male epiproct with two oblong patches of small spines that are of equal size, bare of hairs, lacking grooves.

Species Range
Montana Range Range Descriptions


Range Comments
Known only from the Northern Rocky Mountains in Waterton Lakes National Park, Alberta (Donald and Anderson 1977), south through Glacier National Park into the Mission and Swan Mountains. It is Present on both sides of the Continental Divide in Flathead and Glacier counties at 1610 m to at least 2332 m elevation (Baumann and Kondratieff 2010; Muhlfeld et al. 2011). Populations in Glacier National Park appear to be experiencing local population fragmentation and range contractions, possibly linked to a warming climate (Muhlfeld et al. 2011; Jordan et al. 2016).

Observations in Montana Natural Heritage Program Database
Number of Observations: 275

(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)

No migration is noted for this species, they are restricted in range and dispersal.

The larvae are found in first-order small alpine, mountain streams (Newell and Minshall 1976; Muhlfeld et al. 2011), but only those closely linked to glacial run-off (Giersch 2002).
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Ecological Systems Associated with this Species
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
    Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.  If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Suggested Uses and Limitations
    Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.  These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.  Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).  Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.

    Literature Cited
    • Adams, R.A.  2003.  Bats of the Rocky Mountain West; natural history, ecology, and conservation.  Boulder, CO: University Press of Colorado.  289 p.
    • Dobkin, D. S.  1992.  Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34.  Missoula, MT.
    • Foresman, K.R.  2012.  Mammals of Montana.  Second edition.  Mountain Press Publishing, Missoula, Montana.  429 pp.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998.  Montana atlas of terrestrial vertebrates.  Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT.  1302 p.
    • Hutto, R.L. and J.S. Young.  1999.  Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32.  72 p.
    • Maxell, B.A.  2000.  Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species.  Report to U.S. Forest Service Region 1.  Missoula, MT: Wildlife Biology Program, University of Montana.  161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath.  2004.  Amphibians and reptiles of Montana.  Missoula, MT: Mountain Press Publishing Company. 262 p.

Food Habits
Not described. Most species in the Nemouridae are shredders or collector-gatherers, utilizing coarse plant materials (Merritt and Cummins 1996), which could include mosses growing on the sides of the stream.

The Lednian meltwater stonefly spends most of their life in the aquatic egg and nymph forms and may complete their life cycles in a single year or in 2 to 3 years. Adults are short-lived and emerge from the water to mate on vegetation along the stream by July or August. Ecologically this species is a cold-water stenotherm that is unable to tolerate warm water temperatures (mean temperture exceeding 10 degrees Celsius, maximum temperture exceeding 18 degrees Celsius) and is generally collected within a few hundred meters of the base of glaciers or snow melt derived streams (Muhlfeld et al. 2011).

Reproductive Characteristics
Adults are present and presumably mating takes place in July and August (Baumann et al. 1977, Giersch personal communication).

On October 4, 2016 the U.S. Fish and Wildlife Service proposed listing the Meltwater Lednian stonefly under the Endangered Species Act due to primary to 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
Specific threats to the populations of Lednia are largely related to global warming and the melting of glaciers and their associated snow melt streams. In general, stonefly populations are affected by changes to aquatic habitat such as alteration of flow patterns, streambed substrate, and thermal characteristics. Treanor et al. (2013) predicted chronic temperature maximas.

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Citation for data on this website:
Meltwater Lednian Stonefly — Lednia tumana.  Montana Field Guide.  .  Retrieved on , from