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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


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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. 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 Comments
Known only from the Northern Rocky Mountains in Banff National Park, Alberta, and in and around Waterton-Glacier International Peace Park; in Glacier National Park, Montana, 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: 271

(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).

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 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 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