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Stoneflies - Plecoptera: Chloroperlidae of Gunnison County, Colorado
Sweltsa fidelis - Mountain Sallfly

Banks 1920
Updated 19 Aug 2018
TSN 103286


Sometimes brachypterous (short-winged). Male epiproct indistinguishable from Sweltsa revelstoka, however female subgenital plates are very different. Nymphs were described in 2005, see Stark and Stewart.


Since this species suffered a name change, older publications may refer to this species as Alloperla fidelis.

Good Links

On this website:
Introduction to Sweltsa
Key to Chloroperlidae Nymphs
Key to Chloroperlidae Males
Key to Chloroperlidae Females


Banks,N 1920 New Neuropteroid insects. Bulletin of the Museum of Comparative Zoology. 64: 299-362.
     Described as Alloperla fidelis.

Baumann,RW, Gaufin,AR and Surdick,RF 1977 The stoneflies (Plecoptera) of the Rocky Mountains. Memoirs of the American Entomological Society 31, 1-208. PDF
     Quote from page 179: "This species is abundant in creeks and rivers in the Pacific Northwest. The adults emerge from May to September. "

Delk,JK; Kilgore,MJ; Stark,BP 1998 Comparison of the epiproct structure of two closely related species, Sweltsa fidelis (Banks) and S. revelstoka (Jewett) (Plecoptera: Chloroperlidae). Great Basin Naturalist 58(3) 282-284.
     Abstract: " The male epiprocts of 2 closely related western Nearctic species, Sweltsa fldelis (Banks) and S. revelstoka (Jewett), were examined using SEM. The males of these 2 species have been historically distinguished by epiproct measurements. The ratio of the length from the base to greatest width versus total epiproct length ranges from 0.49 µm to 0.67 µm ( x̄= 0.56) in S. fldelis and 0.55 µm to 0.69 µm (x̄ = 0.60) in S. revelstoka. Similarities in measurement suggest that the location of the greatest epiproct width is not a reliable and consistent character for distinguishing males of these 2 species."

Kondratieff,BC and Baumann,RW 2002 A review of the stoneflies of Colorado with description of a new species of Capnia (Plecoptera: Capniidae). Transactions of American Entomological Society 128 3, 385-401.
     Quote from page 394. "This species occurs in mountain streams, but is not as commonly collected as S. coloradensis or S. lamba. Delk et al. (1998) indicated that males of S. fidelis can not be reliably distinguished from S. revelstoka(Jewett). The latter species is not known from Colorado."

Newell,RL; Baumann,RW and Stanford,JA 2008 Stoneflies of Glacier National Park and Flathead River basin, Montana. International Advances in the ecology, zoogeography, and systematics of mayflies and stoneflies. University of California Publications in Entomology, Berkeley and Los Angeles, pp.173-186.
     The authors note that S. fidelis was the most frequently recorded species out of the 100 different stonefly taxa they collected in their survey of Glacier National park and the Flathead basin in northwestern Montana.

Stark,BP; Stewart,KW 2005 Nymphs of four western nearctic Sweltsa species (Plecoptera: Chloroperlidae). Transactions of American Entomological Society 131 1+2, 189-200.
     Abstract: " Associations were made for four species of western Nearctic Sweltsa nymphs, and a comparative study of selected specimens was initiated to locate characters that might have potential systematic value. Nymphs of S. fidelis (Banks), S. pacifica (Banks), S. revelstoka (Jewett) and S. townesi (Ricker) were successfully distinguished using chaetotaxic features of cerci, mouthparts and femora in combination with pigment patterns of the frons."
Describes characters used to distinguish nymphs of Sweltsa fidelis from S. revelstoka. Has drawings and scanning electron photographs of various little body parts.

Surdick,RF 1985 Nearctic Genera of Chloroperlinae (Plecoptera:Chloroperlidae). University of Illinois Press, Urbana, IL. 146 pages.

Surdick,RF 1995a New western nearctic Sweltsa (Plecoptera: Chloroperlidae). Proceedings of the Entomological Society of Washington 97 1, 161-177.

Brown,WS 2004 Key to the Stoneflies of Gunnison County, Colorado