Stoneflies - Plecoptera: Perlodidae of Gunnison County, ColoradoCultus aestivalis - Summer Springfly(Needham and Claassen 1925)Updated 26 02 2026
TSN 103138 DescriptionOnly later instars can be identified.Life HistoryFuller and Stewart (1977) noted this species is univoltine and emerged from late June to early July in the Gunnison River at Lost Canyon Resort. Possibly large numbers of early instars were present from August thru October, but identification of the tiny nymphs was tentative. Nymphs feed exclusively on Chironomidae, Simullidae and other Dipteran larvae. Chironomid larve in the guts spanned a wide size range suggesting no size selectivity for Chironomidae. Other aquatic insects were absent from the guts.Locations CollectedGunnison River at the Lost Canyon ResortNotesOlder publications may refer to this species as Perla aestivalis.Good LinksOn this website:Other Websites: Photos, Map, Taxon Identifier Numbers - from the Global Biodiversity Information Facility Cultus aestivalis at GBIF Photos, Map, Museums, DNA - Barcode of Life Data System Plecoptera Species File Cultus aestivalis by DeWalt,RE; Hopkins,H; Neu-Becker,U and Stueber,G 2024 ReferencesBaumann,RW, Gaufin,AR and Surdick,RF 1977 The stoneflies (Plecoptera) of the Rocky Mountains. Memoirs of the American Entomological Society 31, 1-208. PDFQuote from page 124: "The genus Cultus is comprised of small to medium -sized stoneflies, yellow in color and lacking all gills and gill remnants. There are one to four crossviens in the costal space of the wing and usually none beyond (fig 53). The mesosternal ridge pattern of both adult and nymph is typical although some nymphs lack the transverse ridge. The lobes of the tenth tergum of the male are short, rounded and spinose(fig 382). The subgenital plate of the female is long and rounded (fig. 384). The three Rocky Mountain species are distinguished on the basis of color pattern, lateral stylets of the males and subgenital plate of the females." Quote from page 124: "This species is common in the creeks and rivers where it has been collected. The adults emerge from April to August. " Fuller,RL and Stewart,KW 1977 The food habits of stoneflies (Plecoptera) in the Upper Gunnison River, Colorado. Environmental Entomology 6, 293-302. Gaufin,AR and Hern,S 1971 Laboratory studies on tolerance of aquatic insects to heated waters. Journal of the Kansas Entomological Society 44:240-245. PDF Abstract: "The mature larvae of fifteen species of aquatic insects (Diptera, Ephemeroptera, Plecoptera, and Trichoptera) and the scud (Amphipoda) were tested to determine their relative sensitivity to heated waters under laboratory conditions. The temperature at which 50% died after 96 hours (TLm96) was recorded as the lethal temperature. This ranged from 11.7 C for the torrential stream mayfly, Cinygmula par Baton, to 32.6 C for the snipefly, Atherix variegata Walker. " They discussed C. aestivalis as Isogenus aestivalis. The TLm96 for C. aestivalis was 16.15°C. 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 397: "This species is especially common in the Colorado River and its larger tributaries. Along the Front Range, C. aestivalis is only known from the Cache la Pudre River in and above Fort Collins. Baumann et al. (1977) reported C. pilatus(Frison) for Larimer County. This record pertains to C. aestivalis." Needham,JG and Claassen,PW 1925 A Monograph of the Plecoptera of North America. Entomological Society of America, Lafayette, Indiana. 397 pages. PDF Described as Perla aestivalis on page 87.  
 
Stewart,KW and Stark,BP 1984 Nymphs of North American Perlodinae genera (Plecoptera: Perlodidae). The Great Basin Naturalist, pp.373-415. PDF  Stewart,KW and Stark,BP 2002 Nymphs of North American Stonefly Genera. 2nd edition The Caddis Press, Columbus, Ohio. 510 pages. Photo of mature nymph patterns on page 107 figure 6.23. Illustrations of nymph on page 385-386, figures 14.15-14.16 Zuellig,RE; Heinold,BD; Kondratieff,BC and Ruiter,DE 2012 Diversity and Distribution of Mayflies (Ephemeroptera), Stoneflies (Plecoptera), and Caddisflies (Trichoptera) of the South Platte River Basin, Colorado, Nebraska, and Wyoming, 1873-2010. U.S. Geological Survey Data Series 606, 257 p. PDF - caution 46MB Quote from page 54: "Within the SPRB this species currently is only known from the Cache la Poudre River near the plains mountain interface from Fort Collins upstream into the foothills. This species likely is more common than these records indicate as it is common in other parts of Colorado (Kondratieff and Baumann, 2002)" The elevation range is 4,950-5,350 feet and the adults emerge from February-June. Illustrations
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