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Stoneflies - Plecoptera: Taeniopterygidae of Gunnison County, Colorado

Taenionema pacificum Pacific Willowfly

(Banks) 1900
Updated 12 August 2023


These insects vary regionally in the branching of wing veins as well as details of size and shape of the lobes on tergum 10, which translated means they're variable and sometimes hard to identify.


Larger streams and Rivers 1600 to 2800 meters elevation (Kondratieff and Baumann (2002).

Life History

Peak emergence is March to May, but later at high elevations in the United States and Canada (Stanger and Baumann, 1993). This species is widely distributed in North America, adults may be collected from mid February to early July. Adults are often found on Salix spp (willow).

Locations Collected

In Colorado, T. pacificum is more common west of the continental divide (Kondratieff and Baumann 2002). Stanger and Baumann (1993) show adults have been collected in Gunnison County from the Gunnison River at Soap Creek, Lake Fork of the Gunnison as well as Cimmarron Creek in Montrose County. Stark et al 1973 records specimens from Soap Creek, Lake Fork Gunnison River, Sapinero Creek, and Quartz Creek.


Stanger and Baumann (1993) comment that there were several sources reporting T. pacificum damaged fruit trees in Washington and Oregon in the early part of the 20th century. They also reported a specimen had eaten Medicago. Older publications may refer to this species as Taeniopteryx pacificum.. Brachyptera (subgenus Taenionema) pacifica is a synonym used in Stark et al 1973. Both genus and species name-ending changed from feminine to neuter (or -a to -um and -is to -e) in the mid 1970s after George Steyskal pointed out the details of the Greek root of the word Taenionema (Steyskal, 1976).

Good Links

On this website:
Key to Taenionema Females
Key to Taenionema Males
Taenionema pallidum

Other Websites:
Photos, Map, Museum specimens, DNA - Barcodinglife.org

Photo - Nymph from Michael Wigle Photography. Nymph again


Banks,N 1900 New genera and species of Nearctic Neuropteroid Insects. Transactions of the American Entomological Society 26:239-259.
     Described as Taeniopteryx pacifica

Baumann,RW; Gaufin,AR; Surdick,RF 1977 The stoneflies (Plecoptera) of the Rocky Mountains. Memoirs of the American Entomological Society 31, 1-208. PDF
     Quote from page 53: "This species is found primarily in rivers in the north but also occurs in streams in the southern part of its range. The adults emerge from March to July."

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 393: "This species is characteristic of larger streams ans rivers throughout the Mountain and Plateau regions of Colorado, usually found at elevations between 1,600-2,800 m. However, it appears to be much more common west of the Continental Divide. Apparently, it occurred historically in several large Front Range streams."

Needham,JG and Claassen,PW 1925 A Monograph of the Plecoptera of North America. Entomological Society of America, Lafayette, Indiana. 397 pages.
     Described as Taeniopteryx pacifica.

Perry,SA; Perry,WB and Stanford,JA 1987 Effects of thermal regime on size, growth rates and emergence of two species of stoneflies (Plecoptera: Taeniopterygidae, Pteronarcyidae) in the Flathead River, Montana. American Midland Naturalist, pp.83-93.
     Abstract: "The life histories of two species of stoneflies were compared in adjacent unregulated and partially regulated reaches of the Flathead River in northwestern Montana. Approximately one-third of the discharge in the partially regulated reach is from the South Fork, which is controlled by a hypolimnial-release dam. Responses of winter-emerging Taenionema pacificum to altered environmental conditions included larger nymphal sizes and altered growth rates and emergence times. Pteronarcella badia, a late-spring emerger, responded with differences in population densities and larger nymphal sizes, but not with significantly altered growth rates or emergence times. Monthly mean temperatures were positively correlated (P < 0.01) with mean specific growth rates of P. badia but not of T. pacificum. Specific growth rates (calculated from measurements of interocular distance) ranged from -0.2% to 2.6%/day for T. pacificum and from -0.1% to 2.5%/day for P. badia. Growth rates differed during the 2 years of the study as a result of varying discharge regimes and weather patterns."

Short,RA; Canton,SP and Ward,JV 1980 Detrital processing and associated macroinvertebrates in a Colorado mountain stream. Ecology, 61(4), 727-732. PDF
     Taenionema nymphs were found in all 4 of the plant species used to make leaf packs; alder, willow, aspen and pine.

Stanger,JA; Baumann,RW 1993 A revision of the stonefly genus Taenionema (Plecoptera: Taeniopterygidae). Transactions of the American Entomological Society 119(3) 171-229.
     A complete diagnosis may be found on page 192 with illustrations on page 225. They discuss regional variation in the size and shape of the lobes on tergum 10 and in the number of branches in the radial sector of the wing. Colorado specimens are larger, have larger quadrate lobes on tergum 10, a rounded epiproct and three to four branches in the radial sector of the wing. Both sexes are macopterous and have heavily sclerotized mandibles and a number of other mouthparts adapted for eating as an adult.

Stark,BP; Oblad,BR; Gaufin,AR 1973 An annotated list of the Stoneflies (Plecoptera) of Colorado Part I. Entomological News 84 (9) 269-277.
     Discussed as Brachyptera (subgenus Taenionema) pacifica.

Stewart,KW 2009 New descriptions of North American Taenionema larvae (Plecoptera: Taeniopterygidae). Illiesia 5(12):128-145. PDF

Stewart,KW 2009 New descriptions of North American Taenionema larvae (Plecoptera: Taeniopterygidae). Illiesia, 5(12), pp.128-145. PDF
     Abstract: "The larvae of Taenionema have been poorly known, with only partial written descriptions and illustrations available for Taenionema kincaidi (Hoppe) and Taenionema pallidum (Banks), prior to the detailed description of Taenionema pacificum (Banks). Larvae of all 13 North American species were associated beginning in 1983, and comparatively studied to test the proposed generic characters, and to determine if they could be separated with external morphological characters. An expanded generic diagnosis, 112 comparative illustrations, and a provisional key to the 13 species are presented. Separation of larvae to species with the key requires a combination of characters of the 9th sternum of males and females, geographic distribution, and the few other species-specific characters."

Stewart,KW; Hassage,RL; Holder,SJ and Oswood,MW 1990 Life cycles of six stonefly species (Plecoptera) in subarctic and arctic Alaska streams. Annals of the Entomological Society of America 83(2)207-214.
     Abstract: Nymphal growth and emergence of adults are described for six species of stoneflies (Plecoptera) found in subarctic and arctic Alaska. The two Nemouridae studied are semivoltine; adults of Zapada haysi (Ricker) are present from May to July and adults of Nemoura arctica Esben-Petersen occur from June to July. The remaining four species are univoltine. Plumiperla diversa (Frison) (Chloroperlidae) has most of its growth occurring during the summer with emergence the following May-September. Taenionema pacificum (Banks) (Taeniopterygidae) completes nymphal growth by the end of January and has an early emergence (April-June). Adults of Arcynopteryx compacta (McLachlan) (Perlodidae) are present from May to August, and growth of nymphs is rapid during summer and fall. Isoperla petersoni Needham ∓ Christenson (Perlodidae) adults are present from June to mid-August, and nymphal growth is interrupted by winter and resumes in the spring; the three other univoltine species studied tend to complete growth before the onset of winter. Growth of these six species is tied to seasonal temperature variation.

Stewart,KW and Stark,BP 2002 Nymphs of North American Stonefly Genera. 2nd edition The Caddis Press, Columbus, Ohio. 510 pages. Illustrations of nymph on pages 239-240, figures 10.9-10.10

Steyskal, GC 1976 Notes on the nomenclature and taxonomic growth of the Plecoptera. pp 408-410. In: A report on the fifth international symposium on Plecoptera. RW Baumann, ed. Proc. Biol. Soc. Wasington. 88:399-428.

Subgenital plate


Tergum 10

nymph leg

Brown,WS 2004 Plecoptera or Stoneflies of Gunnison County, Colorado