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Stoneflies - Plecoptera: Perlodidae of Gunnison County, Colorado

Kogotus modestus - Sickle Springfly

(Banks, 1908)
Updated 24 March 2024

Kogotus modestus nymphs and their reflections. The top stonefly is eating a flatheaded mayfly, the bottom is munching on a small minnow mayfly. Upper East river, early August 2011


Streams and rivers throughout the county.

Local Research Results

K. modestus nymphs have been popular research subjects in the upper Gunnison Basin. Common and easy to catch in the summer, these stoneflies are robust and relatively easy to handle and observe. Both the Peckarsky and Allan Labs at RMBL have worked with this species. The Stewart Lab based out of Texas has published life history data from a population near Pitkin. In fact there are so many papers published on Kogotus, please go to the references to admire them all.

Locations Collected

Copper Creek, Cement Creek, East River, Hall´s Gulch, Hooper Creek


Older publications may refer to this species as Perla modestus or Isogenus modesta.

Good Links

Photos, Map, Museum specimens, DNA - Barcodinglife.org


Allan,J David 1982 Feeding habits and prey consumption of three setipalpian stoneflies (Plecoptera) in a mountain stream. Ecology 63(1), 26-34. Abstract

Allan,JD; Flecker,AS and McClintock,NL 1987 Prey size selection by carnivorous stoneflies. Limnol. Oceanogr. 32(4), 864-872.
      Small stoneflies preyed on small prey and big stoneflies preferred medium sized prey. Percent attacks/encounter by small K. modestus were strongly biased towards small prey, large K. modestus were weakly biased towards large prey. Capture success was greater and handling times were shorter with small prey compared to large prey. To summarize, choice of prey size captured varied with predator size.

Banks,N 1908 Neuropteroid insects - notes and descriptions. Transactions of the American Entomological Society 34:255-267.
     Described as Perla modesta.

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 129: "This species is common in creeks and rivers. The adults emerge from April to August."

Kerans,BL; Peckarsky BL and Anderson,C 1995 Estimates of mayfly mortality: is stonefly predation a significant source?. Oikos 74(2):315-323. PDF
     Abstract: " Field experiments and surveys were carried out in a Rocky Mountain alpine stream during the summers of 1990 and 1992 to estimate the proportion of natural losses of the mayfly Baetis bicaudatus resulting from the co-occurring, predatory stonefly, Kogotus modestus. Functional response experiments determined the number of prey consumed by male and female Kogotus by manipulating the densities of prey and the presence or absence of predators in stream-side chambers. Estimates of losses of Baetis and density of Kogotus were based on ten benthic samples collected weekly (except for last sampling date) from one study reach. Concurrently, drift density of Baetis was estimated upstream and downstream of the reach to determine gains or losses of Baetis resulting from migration. In the functional response experiments Kogotus consumed the same number of prey regardless of prey densities. Female predators tended to consume more prey (~ 2 d-1) than males (~ 1 d-1), although the result was only statistically significant in one out of three experiments. Per-capita mortality rates of Baetis declined from 0.01 to 0.001 d-1 (predator m-2)-1 with increasing prey density. In the study reach Baetis density declined 70% during the 4.5 wk and per-capita losses averaged 3.8% d-1. We estimated that predation by Kogotus could cause between 1.6 and 9.5% of the losses of Baetis from the study reach. This occurred because high losses of Baetis were combined with low consumption rates and densities (1.83 individuals m-2) of Kogotus. Baetis drift density was higher at night than during the day. Drift densities of Baetis tended to be higher leaving than entering the reach in nighttime estimates, although the results were not statistically significant. Few replicates resulted in low power to detect differences in upstream and downstream drift densities; therefore, it is possible that some losses could be the result of drift out of the study reach. Nonetheless our results suggest that Kogotus populations had little direct, lethal effect on Baetis populations in this study reach."

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: "A common species found on the higher elevation small to medium sized streams of the Mountain region. Adults can be collected from July to October."

Larson,EI; Poff,NL; Atkinson,CL and Flecker,AS 2018 Extreme flooding decreases stream consumer autochthony by increasing detrital resource availability. Freshwater Biology, 63(12), pp.1483-1497. PDF
     Quote: "All taxa showed variability in the proportion of their diet derived from autochthonous compared to allochthonous sources across streams (Supplementary Table 1). Generally, mean consumer autochthony ranged from around 0.25 to 0.5 proportionally of the diet. Certain taxa, such as the rhyacophilid caddisfly Rhyacophila angelita (mean of dietary proportion derived from the epilithon of 0.39-0.48 for their prey across streams), the simuliid blackfly Simulium sp. (0.24-0.31), the perlodid stonefly Megarcys signata (0.48-0.53) and nemourid stonefly Zapada sp. (0.51-0.53) varied little in their resource use across streams. In contrast, the baetid mayfly Baetis bicaudatis (0.22-0.52), the perlodid stonefly Kogotus modestus (0.28-0.61), and the ephemerellid mayflies Drunella doddsi (0.26-0.55), and Drunella grandis (0.25-0.42) exhibited more variability in their resource use across streams. Full stable isotope results and biplots are available in Supplemental Figures 1 and 2."

Maketon,M; Stewart,KW; Kondratieff, BC and Kirchner,RF 1988 New descriptions of drumming and evolution of the behavior in North American Perlodidae (Plecoptera). Journal of the Kansas Entomological Society, pp.161-168.
     Abstract: " The drumming behavior of six Plecoptera species, Clioperla clio, Diploperla robusta, Oconoperla innubila, Osobenus yakimae, Perlinodes aurea and Yugus arinus, are described for the first time, and additional data for Isogenoides zionensis are provided. Patterns and evolution of drumming in the family Perlodidae are discussed, and an out-group comparison shows that: (1) a simple call-answer exchange between sexes in seven species is ancestral, and (2) bi-grouped calls of Hydroperla crosbyi and the complex, grouped exchanges of Isogenoides zionensis are derived expressions of drumming. Similarly, grouped calls of some Isoperla and grouped bi-beat calls of Calliperla luctuosa and Kogotus modestus are derived. The grouped drumming pattern is known only in Perlodidae, and the European Leuctra pseudosignifera (Leuctridae)."

Malison,RL; Ellis,BK; DelVecchia,AG; Jacobson,H; Hand,BK; Luikart,G; Woods,HA; Gamboa,M; Watanabe,K and Stanford,JA 2020 Remarkable anoxia tolerance by stoneflies from a floodplain aquifer. Ecology, 101(10), p.e03127. PDF
     Abstract: "Alluvial aquifers are key components of river floodplains and biodiversity worldwide, but they contain extreme environmental conditions and have limited sources of carbon for sustaining food webs. Despite this, they support abundant populations of aquifer stoneflies that have large proportions of their biomass carbon derived from methane. Methane is typically produced in freshwater ecosystems in anoxic conditions, while stoneflies (Order: Plecoptera) are thought to require highly oxygenated water. The potential importance of methane-derived food resources raises the possibility that stonefly consumers have evolved anoxia-resistant behaviors and physiologies. Here we tested the anoxic and hypoxic responses of 2,445 stonefly individuals in three aquifer species and nine benthic species. We conducted experimental trials in which we reduced oxygen levels, documented locomotor activity, and measured survival rates. Compared to surface-dwelling benthic relatives, stoneflies from the alluvial aquifer on the Flathead River (Montana) performed better in hypoxic and anoxic conditions. Aquifer species sustained the ability to walk after 4-76 h of anoxia vs. 1 h for benthic species and survived on average three times longer than their benthic counterparts. Aquifer stoneflies also sustained aerobic respiration down to much lower levels of ambient oxygen. We show that aquifer taxa have gene sequences for hemocyanin, an oxygen transport respiratory protein, representing a possible mechanism for surviving low oxygen. This remarkable ability to perform well in low-oxygen conditions is unique within the entire order of stoneflies (Plecoptera) and uncommon in other freshwater invertebrates. These results show that aquifer stoneflies can exploit rich carbon resources available in anoxic zones, which may explain their extraordinarily high abundance in gravel-bed floodplain aquifers. These stoneflies are part of a novel food web contributing biodiversity to river floodplains."

Needham,JG and Claassen,PW 1925 A Monograph of the Plecoptera of North America. Entomological Society of America, Lafayette, Indiana. 397 pages.
     Discussed as Perla modesta on page 88.

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

Peckarsky,BL 1983 Biotic interactions or abiotic limitations? A model of lotic community structure. In: Dynamics of Lotic Ecosystems. Eds: Fontaine III,Thomas D; Bartell,Steven M Ann Arbor Science, Ann Arbor, Michigan, 303-323.

Kogotus eating a Cinygmula larvae

Peckarsky,BL 1985 Do predaceous stoneflies and siltation affect the structure of stream insect communities colonizing enclosures? Canadian Journal of Zoology 63, 1519-1530.

Peckarsky,BL 1987a Mayfly cerci as defense against stonefly predation: deflection and detection. Oikos 48(2) 161-170.PDF

Peckarsky,BL 1988 Why predaceous stoneflies do not aggregate with their prey. Internationale Vereinigung für Theoretische und Angewandte Limnologie Verhandlungen 23, 2135-2140.
     Investigating optimal foraging theory, she found that contrary to theory K. modestus and Megarcys signata larvae did not hang out in high concentrations of prey.

Peckarsky,BL 1991a A field test of resource depression by predatory stonefly larvae. Oikos 61 (1) 3-10.

Peckarsky,BL 1991b Is there a coevolutionary arms race between predators and prey? A case study with stoneflies and mayflies. n: Menon, J. (Ed.) Trends in Ecology. Council of Scientific Research Integration. Trivandrum, India. 167-180.

Peckarsky,BL 1991c Mechanisms of intra- and interspecific interference between larval stoneflies. Oecologia 85(4) 521-529.
     Abstract: "The purpose of this study was to quantify and compare the behavioral components of the predator-prey interactions between stoneflies and alternative mayfly prey, essential to understanding the reasons for differential rates of predation. This study enables identification of the processes or mechanisms underlying selective predation, and the generation of evolutionary hypotheses to explain why natural selection might favor certain predator behaviors. In situ predation experiments at the East River and Benthette Brook, Gunnison County, Colorado, compared, under near-natural conditions, instantaneous mortality rates due to predation by two species of stream-dwelling stonefly nymphs on different mayfly species. Single-prey experiments predicted relative prey mortality rates in low-density mixed prey assemblages, which we used to test the effects of predator hunger levels and substrate removal on selective predation by stoneflies. One stonefly species, Megarcys signata, consistently selected Baetis bicaudatus over Cinygmula mimus and Ephemerella infrequens in single-prey and mixed-prey trails, when starved for 6 d, 1 d, or fed prior to experiments, and when natural substrates were present or absent. However, substrate removal increased Cinygmula's absolute mortality rate, resulting in significant selectively on this species over Ephemerella. The other stonefly species, Kogotus modestus, selectively consumed either Baetis or Epeorus deceptivus over Cinygmula, depending on the experimental conditions. While Kogotus hunger levels did not affect differential prey mortality, substrate removal resulted in selection of Baetis over Epeorus, and increased absolute mortality rates of all three prey species. These data show that substrate removal can alter patterns of selective predation, which we attribute to differential effects of refuges on predator encounter rates with different prey types. To determine mechanisms underlying observed patterns of selective predation, we videotaped behavioral interactions between predators and prey under simplified field conditions that enabled careful observation. With no substrate present, predator-prey encounter rates and captures per attack were equivalent among prey types (except for Ephemerella, which was never captured). However, both starved and fed predators showed significantly higher probabilities of attack per encounter with Baetis than with any other mayfly species, which resulted from Baetis' hydrodynamically conspicuous swimming motion acting as a proximal attack stimulus. These data suggest that selective predation by stoneflies is more a consequence of active behavioral selection than of prey vulnerability since the probability of attack given an encounter was not constant across all prey types. However, we contend that prey defensive behavior and morphology affect not only encounter rates and capture success, but also attacks per encounter, because prey that did not swim were attacked less per encounter than were prey that swam. Also, although we did not observe significant differences among prey types in encounter rates or captures per attack, a multiple regression analysis showed that these factors, in addition to attacks per encounter, contributed significantly to observed variation in capture rates among prey types in behavioral trials. Thus, we conclude that differential prey vulnerability or fixed behavioral selection is a more probable proximate cause of selective predation than is active behavioral selection, since stoneflies showed a fixed attack response to swimming prey. Finally, we stress that this mechanism of selective predation may or may not result in optimal foraging from an energy maximization standpoint, depending on the direction of competing selection pressures."

Peckarsky,BL 1996 Alternative predator avoidance syndromes of stream-dwelling mayfly larvae. Ecology, 77(6) 1888-1905. PDF
     Abstract: "Experiments were conducted to compare the patterns, mechanisms, and costs of predator avoidance behavior among larvae of five species of mayflies that co-occur with the predatory stoneflies, Megarcys signata and Kogotus modestus in western Colorado streams. Mayfly drift dispersal behavior, use of high vs. low food (periphyton or detritus) patches, microhabitat use, positioning, and activity periodicity were observed in the presence and absence of predators in circular flow-through chambers using natural stream water. Also, distances from predators at which prey initiated escape responses were compared among prey and predator species. Costs of predator avoidance behavior were assessed by measuring short-term (24 h) feeding rates of mayflies in the presence or absence of predatory stoneflies whose mouthparts were immobilized (glued) to prevent feeding. The intensity and associated costs of predator avoidance behavior of mayfly species were consistent with their relative rates of predation by stoneflies. Megarcys consumes overwintering generation Baetis bicaudatus > Epeorus longimanus > Cinygmula = Ephemerella; Kogotus consumes summer generation Baetis > Epeorus deceptivus = Cinygmula; Megarcys eats more mayflies than Kogotus. While Megarcys induced drift by Baetis, Epeorus, and Cinygmula, this disruptive predator avoidance behavior only reduced food intake by Baetis and Epeorus. The morphologically defended mayfly species, Ephemerella, neither showed escape behavior from Megarcys, nor any cost of its antipredatory posturing behavior. Only Baetis responded by drifting from Kogotus. No mayfly species shifted microhabitats or spent less time on high-food patches in the presence of foraging stoneflies. However, predators enhanced the nocturnal periodicity of Baetis drift, which was negligible in the absence of stoneflies as long as food was abundant. Lack of food also caused some microhabitat and periodicity shifts and increased the magnitude of both day and night drift of Baetis. Thus, Baetis took more risks of predation by visual, drift-feeding fish not only in the presence of predatory stoneflies, but also when food was low or they were hungry. All other mayflies were generally nocturnal in their use of rock surfaces, as long as food was abundant. Finally, the distances at which different mayfly species initiated acute escape responses were also consistent with relative rates of predation. This study demonstrates alternative predator avoidance syndromes by mayfly species ranging from an initial investment in constitutive morphological defenses (e.g., Ephemerella) to induced, energetically costly predator avoidance behaviors (e.g., Baetis). Although the costs of Ephemerella's constitutive defense are unknown, experiments show that prey dispersal is the mechanism underlying fecundity costs of induced responses by Baetis to predators, rather than microhabitat shifts to less favorable resources or temporal changes in foraging activity. A conceptual model suggests that contrasting resource acquisition modes may account for the evolution and maintenance of alternative predator avoidance syndromes along a continuum from Baetis (high mobility) to heptageniids (intermediate mobility) to Ephemerella (low mobility). Prey dispersal (swimming) to avoid capture results in reduction of otherwise high fecundity by Baetis, which trades off morphological defense for enhanced ability to acquire resources. Thus, improved foraging efficiency is the selection pressure maintaining the highly mobile life style in Baetis, which increases resource acquisition and fecundity, offsetting the high mortality costs associated with this behavior."

Peckarsky,BL; Cowan,CA 1991 Consequences of larval intraspecific competition to stonefly growth and fecundity. Oecologia 88, 277-288.

Peckarsky,BL and Cowan,CA 1995 Microhabitat and activity periodicity of predatory stoneflies and their mayfly prey in a western Colorado stream. Oikos 73(4) 513-521. PDF
     Abstract: " Experiments were conducted to determine whether overlap between microhabitat preferences and activity periodicities of four mayfly species and their stonefly predators could explain species-specific differences in predator-prey encounter frequencies. Preferences for rock type (slate or granite), flow microhabitat (high or low), rock surface (top, bottom, upstream or downstream sides), and periodicity of drift and the use of rock tops were measured in a stream-side system of flow-through circular Plexiglas chambers receiving natural stream water and light levels. These parameters were compared among the predatory stoneflies, Megarcys signata or Kogotus modestus, and four species of mayflies that vary in their encounter rates with the stoneflies. Based on predator-prey encounter rates previously observed in similar chambers, we expected greater overlap between Megarcys and Ephemerella infrequens and the overwintering generation of the bivoltine mayfly, Baetis bicaudatus than with Cinygmula sp. Likewise, we expected Kogotus microhabitat use to overlap more strongly with that of summer generation Baetis than with later instars of Cinygmula and Epeorus deceptivus. Results ran counter to our predictions, indicating that microhabitats of the prey species with high predator encounter rates did not overlap more strongly with the stoneflies than did mayflies with low predator encounter rates. Most mayflies and stoneflies preferred the bottom surfaces of granite rocks, and showed few flow preferences. Most were nocturnal in their use of top rock surfaces, in drift and feeding activity periodicity. Therefore, nocturnal activity periodicities of both mayflies and stoneflies confirm that mayflies have not evolved feeding periodicity to avoid encounters with foraging stonefly predators. We conclude therefore, that neither temporal nor spatial microhabitat overlap is a reasonable explanation of differential encounter rates between predatory stoneflies and their mayfly prey. Alternative explanations for differential encounter rates are that more abundant or more mobile mayflies have higher encounter rates with predators, and effective pre-contact predator avoidance responses of other mayflies reduce their encounter rates with stoneflies."

Peckarsky,BL; Cowan,CA; Penton,MA and Anderson,CR 1993 Sublethal consequences of stream-dwelling predatory stoneflies on mayfly growth and fecundity. Ecology 74 6, 1836-1846.
     Abstract: "Predators can have consequences on prey populations and communities that extend well beyond direct predator-induced mortality. Predator-prey interactions often affect prey feeding rates, growth rates, or fecundities, thereby significantly affecting reproductive success of prey adults. Thus, investigation of the sublethal fitness consequences of behavioral responses of prey to predators is essential to our understanding of the total impact of predators on prey populations and communities. Feeding (algal grazing) rates, growth rates, and fecundities of Baetis bicaudatus (Baetidae) larvae were measured in replicated circular flow-through stream channels to determine the sublethal consequences on fitness correlates of the presence of predatory stoneflies (Perlodidae). Gut fullness of 24-h starved Baetis larvae was measured using fluorometry after 24 h (short-term experiments) in four treatments: (1) ambient resource rocks and no predators, (2) low resource rocks and no predators, (3) ambient resource rocks and one female perlodid stonefly (Megarcys signata), or (4) Kogotus modestus whose mouthparts were glued to prevent lethal effects of predation. Mid-instar male and female Baetis larvae were reared for 3 wk until wing pad maturation (long-term experiments) and subjected to all but the Kogotus treatment. Predator avoidance significantly reduced levels of Baetis gut fullness, over the short term, to levels intermediate between the high and low resource treatments. Longer term residence with predatory stoneflies caused larvae of both male and female Baetis to mature at significantly smaller sizes than in the treatment with ambient food but no predators. Mayflies with predators matured at sizes similar to those held with low food levels over the long term. Interestingly, both starved larvae and those avoiding predators did not grow during the experimental period in contrast to about a 50% growth rate of larvae experiencing ambient food levels, but no predators. Similarly, egg biomass per mature female larva was significantly reduced in both starved and predator treatments. The proportion of total body mass allocated to eggs was only reduced in starved mayflies indicating that the females avoiding predators accrued less total mass, but allocated a similar proportion to eggs as did well-fed Baetis. These data convincingly demonstrate that predator avoidance can have dramatic consequences on mayfly fitness. The mechanism explaining those fitness consequences is probably a disruptive drift/swim response by Baetis to encounters with stoneflies, which reduces Baetis' feeding rates. If we accept the assumption that natural selection has shaped the foraging behavior of organisms to maximize fitness, foragers need to make decisions that maximize both survivorship (minimizing risk of predation) and fecundity. In mayflies fecundity is entirely a function of resource acquisition by the larvae, which makes them particularly vulnerable to such sublethal effects of predation. Nonetheless, we suspect that the types of sublethal costs of predator avoidance documented by this and other recent studies are nearly universal consequences or organisms foraging under predation risk."

Peckarsky,BL and Dodson,SI 1980 An experimental analysis of biological factors contributing to stream community structure. Ecology 61 6, 1283-1290.

Ricker,WE 1992 Origin of stonefly names proposed by Ricker and collaborators. Perla, 18(1) 12 pages. PDF
      Quote from page 6: "Kogotus Ricker 1952 (as sg. of Isogenus). Russian kogot =claw or nail. Refers to the lobe on the 7th sternite of the male. "

Ruse,LP and Herrmann,SJ 2000 Plecoptera and Trichoptera species distribution related to environmental characteristics of the metal-polluted Arkansas River, Colorado. Western North American Naturalist 60 (1) 57-65. PDF
     They looked at the Arkansas River above and below some notorious heavy metal mine pollution sources, California Gulch and the Leadville Drain. They found that adult Kogotus were eliminated by the Leadville Drain, recovered and reappeared a ways downstream, then were present below California Gulch at one site before disappearing for good. After freshwater was added to the Arkansas River from the western slope, Kogotus reappeared at one site. They were probably missing farther downstream due to warmer water temperatures and would have been missing from a clean river as well.

Stanford,JA and Ward,JV 1989 Serial discontinuities in a Rocky Mountain river. I. Distribution and abundance of Plecoptera. Regulated Rivers: Research and Management 3, 169-175.

Stewart, KW and Sandberg, JB 2003 The life history of a Colorado population of Kogotus modestus Research Update on Ephemeroptera and Plecoptera E. Gaino (Ed.) University of Perugia, Perugia Italy pp.195-200. PDF available on Sandberg's website
     They studied Kogotus in Hooper Creek and Halls Gulch near Pitkin. They observed a synchronized emergence of adults in late August and early September. They include scanning electron micrographs of K. modestus eggs and lacinia (a mouthpart). Looking at the gut contents of 30 larvae, they found that K. modestus ate almost entirely Chironomid larvae. The males stopped feeding before emerging, while the females kept eating. They tested the eggs for diapause and found that the eggs diapause through at least the first winter and hatch in the spring, while other eggs diapaused longer and hatched the following spring.

Vance,SA and Peckarsky,BL 1997 The effect of mermithid parasitism on predation of nymphal Baetis bicaudatus (Ephemeroptera) by invertebrates. Oecologia 110, 147-152.
     They found that Kogotus modestus ate significantly more parasitized than unparasitized B. bicaudatus. However, Rhyacophila hyalinata caught and ate equal numbers of parasitized and unparasitized nymphs. They attribute this to the behavior of parasitized nymphs and different hunting behaviors of the predators. Parasitized nymphs drifted less, which increased encounter rates with Kogotus nymphs. However R. hyalinata larvae are ambush predators and catch parasitized and unparasitized nymphs equally. They hypothesize that avoiding fish predation by drifting less is a greater advantage to the parasite than the losses suffered by increased stonefly predation.

Mesosternal Y-arms.
Only visible easily on mature nymphs.

Brown,WS 2004 Stoneflies of Gunnison County, Colorado