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Stoneflies - Plecoptera: Nemouridae of Gunnison County, Colorado

Prostoia besametsa
Banded Forestfly, Tiny Winter Blacks

(Ricker 1952)
Updated 12 Jan 21
TSN 102585


Nymphs are 5-6mm long, brown to dark brown, with a lighter colored ventral side. Gills are absent. Older nymphs can be sexed, look for developing male genitalia on sternum 9 of males and a hint of a subgenital plate for mature female larvae. Knight and Gaufin found that P. besametsa was a cold stenotherm (restricted to cold water), found only at higher elevations in their study of streams in the Gunnison Basin. Hassage and Stewart found that Prostoia besmeta nymph densities were an order of magnitude higher in leaf packs than in mineral substrates. Nymphs grew during the winter until adults emerged in early spring. Eggs laid in the spring diapaused until Oct-Jan, starting their life cycle again.

Locations Collected

Stark, Oblad and Gaufin (1973) collected this species in the Taylor River, East Fork of Cimarron Creek, Gunnison River and Sapinero Creek. Knight and Gaufin collected P. besametsa from 8700-9500 feet in the South Fork of the Gunnison Drainage during the early 1960's. This is one of the most common stoneflies in Colorado.


The genus Prostoia was previously included in Nemoura. Older publications may refer to this species as Nemoura besametsa.

Good Links

On this website:
Introduction to the Nemouridae

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

Photo - Nymph from Michael Wigle Photography. More photos: Nymph 2 Nymph 3 Adult

Photo - from BugGuide.net


Baumann,RW, Gaufin,AR and Surdick,RF 1977 The stoneflies (Plecoptera) of the Rocky Mountains. Memoirs of the American Entomological Society 31, 1-208.
     Quote from page 38: " This species is common in creeks and small rivers throughout its range. The adults emerge from March to August. " They show P. besametsa present in Gunnison County, Colorado.

Canton,SP and Ward,JV 1981 The aquatic insects, with emphasis on Trichoptera, of a Colorado stream affected by coal strip-mine drainage. Southwestern Naturalist 25 4, 453-460.
     They studied Trout Creek where it runs through the Edna Coal Mine in northwestern Colorado. The mine spoils were 30 meters from the edge of the creek (approximately a 100 foot buffer zone). They found the aquatic insect density (numbers per square meter) and biomass (weight in grams per square meter) did not change above and below the mine. The Shannon-Weaver Diversity index also showed no difference between sites. However the community structure (which species were present and proportions) did change. Since there were irrigation water and cattle influences at their downstream site, their results may reflect these additional water uses. They note the biggest visible change at this mine is the loss of willow and alder trees downstream of the mine. The caddisfly population changed the most between sites, shifting from a mix of families above the mine to dominance by Hydropsychidae and Glossosomatidae below the mine.
Prostoia besametsa was most common at the clean, forested, shaded, upstream site. It was probably more common here partly because it is a shredder and needs leaves to eat.

Grubbs,SA; Baumann,RW; DeWalt,RE and Tweddale,T 2014. A review of the Nearctic genus Prostoia (Ricker)(Plecoptera, Nemouridae), with the description of a new species and a surprising range extension for P. hallasi Kondratieff and Kirchner. ZooKeys, 401: 11-30. html
     Abstract: "The Nearctic genus Prostoia (Plecoptera: Nemouridae) is reviewed. Prostoia ozarkensis sp. n. is described from the male and female adult stages mainly from the Interior Highland region encompassing portions of Arkansas, Missouri, and Oklahoma. Prostoia ozarkensis sp. n. appears most closely related to two species, one distributed broadly across the western Nearctic region, P. besametsa (Ricker), and one found widely throughout the central and eastern Nearctic regions, P. completa (Walker). A surprising range extension is noted for P. hallasi Kondratieff & Kirchner, a species once known only from the Great Dismal Swamp, from small upland streams in southern Illinois. Additional new state records are documented for P. besametsa, P. completa, P. hallasi and P. similis (Hagen). Taxonomic keys to Prostoia males and females are provided, and scanning electron micrographs of adult genitalia of all species are given."

Hassage,RL 1989 Life histories, behavior and space partitioning in selected species of western North American Plecoptera. pHd Dissertation, University of North Texas. 105pgs. PDF
     Abstract: "Five species of stoneflies (Zapada haysi, Plumiperla diversa, Taenionema pacificum, Isoperla petersoni, Arcynopteryx compacta) from the North Slope and Interior of Alaska were examined for seasonal patterns of emergence of adults and growth of nymphs. Generally growth was retarded during the winter in this region, and all species except I. petersoni completed growth prior to January. The life cycles of six stonefly species (Prostoia besametsa, Triznaka signata, Sweltsa coloradensis, Isoperla fulva, Skwala parallela, Claassenia sabulosa) are described from northern New Mexico. In this region growth was generally less retarded during the winter than in Alaska; P. besametsa completed all nymphal growth during late fall and winter. Drumming behavior of a Colorado population of Pteronarcella badia was described using an evolutionary framework to explain the maintenance of signal variation in this species. Laboratory experiments were used to explore the effect of intraspecific and interspecific interactions on spatial partitioning in P. badia and Claassenia sabulosa. P. badia exhibited clumping and distributed itself as the surface area of substrate in low densities; however, in the presence of C. sabulosa its distribution was random and different from available surface area. A field study was used to examine spatial partitioning by three New Mexico stonefly species (I. fulva, P. besametsa, T. signata) and to ascertain patterns of microdistribution relating to several abiotic and biotic factors. Generally, there was an interaction of the measured abiotic parameters (current, water temperature, time) with nymphal size. Additionally, void space and sample volume were successfully used to compare biotic densities among leaf and mineral substrates, which were higher in leaf packs than in mineral substrates."

Hassage,RL and Stewart,KW 1990 Growth and voltinism of five stonefly species in a New Mexico mountain stream. The Southwestern Naturalist, 35 (2)130-134. Abstract and first page

Kiffney,PM 1996 Main and interactive effects of invertebrate density, predation, and metals on a Rocky Mountain stream macroinvertebrate community. Can. J. Fish. Aquat. Sci. 53(7): 1595-1601.

Knight,AW; Gaufin,AR 1966 Altitudinal distribution of stoneflies (Plecoptera) in a Rocky Mountain drainage system. Journal of the Kansas Entomological Society 39 4, 668-675.

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 392: " This is one of the most common stonefly species in Colorado. It is widely distributed throughout the state, associated with medium to large Mountain streams."

Nelson,SM and Roline,RA 1999 Relationships between metals and hyporheic invertebrate community structure in a river recovering from metals contamination. Hydrobiologia 397, 211-226.

Radford, DS and Hartlan-Rowe,R 1971 The life cycles of some stream insects (Ephemeroptera, Plecoptera) in Alberta. Canadian Entomologist 103: 609-617
     They studied P. besametsa as Nemoura besametsa on the eastern slopes of the Rocky Mountains in Alberta, Canada. P. besametsa mostly emerged from mid April to mid-June, with a few more adults found in July.
Quote from page 611: "The eggs of N. besametsa are laid in the spring and eary summer; however, it is not until 7 or 8 months later that nymphs about 2mm in length appear. A diapause is likely responsible. These nymphs grow rapidly to complete their development by April or May. "

Ricker, W.E. 1952. Systematic studies in Plecoptera. Indiana University Publications, Science Series 18, 200 pages, Bloomington, Indiana.

Ricker,WE 1992 Origin of stonefly names proposed by Ricker and collaborators. Perla, 18(1) 12 pages. PDF
      Quote from page 9: "Prostoia Ricker 1952 (as sg. of Nemoura). Russian prostoi = simple, referring to the uncomplicated epiproct. besametsa (Ricker 1952) - as Nemoura (Prostoia). Russian bez = without, samets = male. For several years I had many female specimens but no males. "

Stewart,KW and Ricker,WE 1997 The stoneflies of the Yukon. pgs 201-222 in Danks,HV and Downes,JA (Eds.), Insects of the Yukon. Biological Survey of Canada (Terrestrial Arthropods), Ottawa. 1034 pp.
     Quote about the genus Prostoia from page 210: "Nearctic; 3 of the 4 Nearctic species are found in the east, with only Prostoia besametsa found widely distributed in the west, from Alaska and Yukon to California and New Mexico. Adults dark, 5-6 mm, emerging February-March in the Ozark Mountains to March-August at northern latitudes. The herbivorous/detritivorous nymphs are found mainly in coarse particulate organic matter in small streams, and species studied have univoltine, fast life cycles. "

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

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