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Introduction to the Stoneflies (Plecoptera)
of Gunnison County, Colorado, USA

Updated 12 Apr 2021

What is a Stonefly?

Stoneflies are aquatic insects who live in streams and rivers during their egg and nymph stages. After emerging out of the water as adults, they signal the opposite sex by drumming or just chasing each other about on the banks and riparian vegetation near the stream. Stoneflies are found throughout the temperate zone on most continents. The fancy scientific name for this order of insects is Plecoptera which means twisted or folded (Pleco) wing (optera). The earliest stonefly fossils have been found in 260 million year old Permian rocks.

Stoneflies are common in mountainous areas with clean water. They are the "P" in the popular macroinvertebrate metric %EPT. In our area, mining has caused the disappearance of stoneflies (and the other aquatic insects) from all the orange-red streams you see contaminated with acid mine drainage. However, researchers working in the Arkansas River near the Superfund site by Leadville Colorado have found that a few species of stoneflies are quite tolerant of heavy metals. In fact, stoneflies are good indicators of water quality since they disappear immediately after exposure to some kinds of pollution. Plecoptera are among the first macroinvertebrates to disappear in rivers contaminated with sewage.

Most of the upper Gunnison Basin is good habitat in excellent condition. Since fish eat stoneflies, our vigorous stonefly population helps to support the fishing industry. People who fish, boat or live near a stream or river spend a lot of time in stonefly habitat and are often quite aware of our local stonefly community.

Life History

Stonefly life histories are very flexible. As eggs, they may diapause and wait until more favorable environmental conditions. After hatching most species forage on the rocks in cold, clean streams and rivers. Some will enter diapause as a nymph in the hyporheic zone of the stream bed. Some nymphs live in leaf packs and eat detritus, but many are predatory and eat the other bottom dwellers, while predictably other species are omnivorous. Its also common for stoneflies to change their diet as they grow up or as the availability of food fluctuates. Some stoneflies spend part of their time in the hyporheic zone, which is the streambed or groundwater below the river bottom. All species molt or shed their exoskeleton a number of times growing in stages called instars.

Eventually the nymphs emerge as terrestrial adult stoneflies. The adults either climb about in vegetation near the water or scramble among the rocks on the bank looking for mates. Stonefly adults communicate by drumming their abdomen on the branch or ground. The males call the females, who often respond with their own drumming. The pair sing or drum for a while in a duet that often ends in mating. The female may lay her eggs right away or live for a while in the riparian zone and lay her eggs later.

In some species the adults may all emerge over a few weeks (synchronously) or they may emerge for months (asynchronously). The length of time it takes to get from an egg thru nymph to adult and back to egg varies from species to species and may be one year or up to 3 or 4 years for some of the bigger predatory species. Males are usually smaller than females in all lifestages. (Stewart and Stark, 2002). In the Rio Conejes River southeast of Gunnison County, most adult stoneflies emerged right around the summer solstice (DeWalt and Stewart, 1995).

Stonefly eggs. We found these under a rock in the East River near Gothic in July 2012.

Local Researchers

One of the early stonefly researchers at The Rocky Mountain Biological Lab (RMBL)) was J. David Allan. He published an altitudinal survey of Cement Creek that is still widely cited. With graduate students such as Nancy McClintock, Alex Flecker and Brian Fiefarek he unraveled some of the mysteries of mayfly swarming and drift behavior. Dave used Copper Creek near Gothic and Cement Creek for some of his experiments. Lab based predator-prey interactions between stoneflies such as Kogotus modestus and prey such as Baetis bicaudatis or Simuliidae were fruitful. Dave moved to the University of Michigan in 1991 and has been working in the midwest ever since. He has switched to land use and landscape scale effects of human activities on water resources.

Starting in the 1970s, a prolific Bobbi Peckarsky began a long career studying the aquatic insects of the East River and other steams near Gothic and RMBL. Recently her major collaborators have been Angus McIntosh, Andrea Encalada, Brad Taylor, Maruxa Alvarez and Kara Cromwell among many other students and colleagues. They have published many widely cited studies on the stoneflies Megarcys signata, Kogotus modestus and the mayflies Baetis bicaudatus and Epeorus deceptivus among many other aquatic macroinvertebrates.

Meanwhile Ken Stewart and Kevin Alexander worked in the Gunnison River downstream of Almont, Colorado. They revised the stonefly genus Suwallia, among other things.

James Ward and collaborators have worked on the effects of dams in the Gunnison River Basin.

Brad Taylor is working with stoneflies and recently Didymosphenia, the nuisance algae while bringing in new stonefly researchers.

Good Links

On this website:
Introduction to various Stonefly families:
Capniidae - Small Black Winter Stoneflies
Chloroperlidae - Little Green or Yellow Stoneflies
Leuctridae - Rolled Wing Stoneflies
Nemouridae - Winter Stoneflies
Perlidae - Big Golden Stones
Taeniopterygidae - Willow or Winter Stoneflies

Other Websites:
  • Plecoptera Species Files

  • Photos - and an excellent Introduction to Stoneflies by Riley Nelson on the Tree Of Life website.

  • Illiesia - an online Journal dedicated to stoneflies.
         The illustrations, whether they are scanning electron micrographs, photos, maps, graphs or any of the other usual science stuff, are beautiful to behold :-)

  • Plecoptera Page by Gordon Ramel.

  • Maps - Boris Kondratieff and Richard Baumann (coordinators). 2000. Stoneflies of the United States. Jamestown, ND: Northern Prairie Wildlife Research Center Online. (Version 12DEC2003). archived on the Way Back Machine

  • Wikipedia


Allan, J.D. 1975a. The distributional ecology and diversity of benthic insects in Cement Creek, Colorado. Ecology 56(5) 1040-1053. Abstract

Allan,JD 1982 Feeding habits and prey consumption of three setipalpian stoneflies (Plecoptera) in a mountain stream. Ecology 63 1, 26-34. Abstract
     The maximum meal size for a stonefly is approximately 10% of their dry mass. Stonefly diets varied from site to site in an elevational survey of stonefly diets in Cement Creek. In spite of this, most of the smaller stoneflies ate diatoms and chironomids as their main prey item and switched to Baetis bicaudatis and other Ephemeroptera in the larger instars. Lesser numbers of Simuliidae, Plecoptera and Trichoptera were also found in the guts of larger stoneflies. The diet shift occurred at about 10mg of body size in Cement Creek among Megarcys signata and Kogotus modestus.

DeWalt,RE and Ower,GD 2019 Ecosystem services, global diversity, and rate of stonefly species descriptions (Insecta: Plecoptera). Insects, 10(4), p.99. PDF

DeWalt,RE and Stewart,KW 1995 Life histories of stoneflies (Plecoptera) in the Rio Conejos of southern Colorado. Great Basin Naturalist 55, 1-18. PDF
     Has life histories of many of the species living in the Gunnison Basin.

Fochetti,R and De Figueroa,JMT 2007 Global diversity of stoneflies (Plecoptera; Insecta) in freshwater. In Freshwater Animal Diversity Assessment (pp. 365-377). Springer, Dordrecht. PDF

Fuller,RL and Stewart,KW 1977 The food habits of stoneflies (Plecoptera) in the Upper Gunnison River, Colorado. Environmental Entomology 6, 293-302.
     They found a higher proportion of empty guts in stoneflies during peak runoff in the Gunnison River. Sometimes the stoneflies go hungry during the spring melt.

Heino,J 2011 A macroecological perspective of diversity patterns in the freshwater realm. Freshwater Biology, 56(9), pp.1703-1722.
     Abstract: "The present distributions of stonefly genera in North America, their occurrence as endemics, or as shared with the Far East, Europe and South America, are considered in conjunction with geological history. It is concluded that the Plecoptera of North America have four sources of origin.There was an ancient eastern fauna shared with Europe before the formation of the North Atlantic Ocean. A second group moved in from the west during the formation of the western mountains. After formation of the isthmus one genus moved northward from South America. After the Pleistocene period several species migrated from the Bering Strait region, possibly from an Alaskan refugium. Some of these have clearly moved eastward, but a few may have moved westward."

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. JSTOR first page
     They noted that omnivorous stoneflies have the greatest altitudinal range. They also found that to some extent larger stoneflies are found in larger rivers.

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.
     Abstract:"Eighty-six species of stoneflies are reported from Colorado, including a new species of Capnia. Three new state records are reported, IBolshecapnia milami (Nebeker and Gaufin), Capnura fibula (Claassen), and Isoperla marlynia (Needham and Claassen). Ninety percent of all Colorado stoneflies are typical western North American species, with seven species, Paracapnia angulata Hanson, Taeniopteryx burksi Ricker and Ross, T. parvula Banks, I. marlynia, Acroneuria abnormis (Newman), Perlesta decipiens (Walsh), and Isoperla bilineata (Say) having eastern affinities. Arcynopteryx compacta (McLachlan) is considered circumpolar species."

Peckarsky,BL 1980 Predator-prey interactions between stoneflies and mayflies: behavioral observations. Ecology 61(4) 932-943. Abstract

Peckarsky, BL and Dodson,SI 1980. An experimental analysis of biological factors contributing to stream community structure. Ecology 61:1283-1290. Abstract

Stewart,KW and Stark,BP 2002 Nymphs of North American Stonefly Genera. 2nd edition The Caddis Press, Columbus, Ohio. 510 pages.
     The bible of stonefly identification. Also reviews the scientific literature for many species. There are beautiful photos as well.

Zwick,P 2000 Phylogenetic system and zoogeography of the Plecoptera. Annual review of entomology, 45(1), pp.709-746.
     Abstract: " Information about the phylogenetic relationships of Plecoptera is summarized. The few characters supporting monophyly of the order are outlined. Several characters of possible significance for the search for the closest relatives of the stoneflies are discussed, but the sister-group of the order remains unknown. Numerous characters supporting the presently recognized phylogenetic system of Plecoptera are presented, alternative classifications are discussed, and suggestions for future studies are made. Notes on zoogeography are appended. The order as such is old (Permian fossils), but phylogenetic relationships and global distribution patterns suggest that evolution of the extant suborders started with the breakup of Pangaea. There is evidence of extensive recent speciation in all parts of the world."

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