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Trichoptera: Hydropsychidae of Gunnison County, Colorado

Arctopsyche grandis
Great Grey Spotted Sedge, McKenzie Caddis

(Banks) 1900

Updated 22 June 2021
TSN 115530

Many Arctopsyche larvae were found during the summers of 2007 and 2008 in the East River Didymosphenia bloom. There are larval retreats for several larval instars in the photo. Look for cave like holes.


The larvae of this large Hydropsychid caddisfly are very common in the East River near and above Gothic. It has two color morphs. Some animals have a white-striped head and some have a brown head without the stripe. Most kick samples from the East River will have an Arctopsyche larvae or maybe 10 of them. Gently overturning rocks in the stream allows you to see Arctopsyche larvae in their retreats, you may be able to see their nets as well. Arctopsyche larvae adapting to a Didymosphenia geminata bloom in the East River.

Good Links

On this website:
Arctopsyche inermis
Introduction to the Hydropsychidae

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

Illustration - University of Alberta Entomology Collection Species page
     Has illustration of male genitalia, description, habitat information, range and more.

Locations Collected

Common and widespread. The Illinois Natural History Survey (INHS) Database shows this species is present 1 mile below Ohio, which probably means Ohio City and Ohio Creek. In my collection and experience A. grandis is found in the East River near Gothic, East River above confluence with Cement Creek, Cement Creek, Coal Creek, Copper Creek, Rustlers Gulch, Brush Creek, Taylor River, Gunnison River at McCabe Lane, and Willow Creek in Taylor Park. It is undoubtably present in many other streams in the County.


Alstad,DN 1980 Comparative biology of the common Utah Hydropsychidae (Trichoptera). American Midland Naturalist 103, 167-174.

Banks,N 1900. New genera and species of Nearctic neuropteroid insects. Transactions of the American Entomological Society 26:239-260.
     Described in the genus Hydropsyche.

Blackadar,RJ; Baxter,CV; Davis,JM and Harris,HE 2020 Effects of river ice break-up on organic-matter dynamics and feeding ecology of aquatic insects. River Research and Applications, 36(3) 480-491. PDF
     Abstract: "Disturbance shapes the structure and function of aquatic communities and ecosystems, but the dynamics of ice are a less studied dimension of the disturbance-regime of rivers. We investigated effects of a river-ice regime on organic-matter dynamics and feeding ecology of aquatic insects. Samples of biofilm and aquatic insects for gut content analysis were collected monthly from Big Creek, a sixth - order tributary of the Middle Fork Salmon River in central Idaho, USA, during winter 2010-2011. Our results indicate that river ice affects both quantity and quality of organic matter available to, and used by, consumers. Specifically, scour from December and February ice break-up events reduced biofilm biomass by one-half and one-third, respectively, whereas quality (chlorophyll-a: ash-free dry mass) increased. Diets of scrapers, Rhithrogena (Heptageniidae) and Bibiocephala (Blephariceridae), collector-gatherers, Baetis (Baetidae), and collector-filterers, Simulium (Simulidae) appeared to follow patterns of organic matter. Following ice break-up events, diets of these taxa had increased proportions of diatom frustules, which are high-quality food resources due to their relatively high nutrient content. Other taxa, such as collector-gatherers, non-Tanypodinae (Chironomidae), and the collector-filterer, Arctopsyche grandis (Hydropsychidae), consistently consumed high proportions of diatom frustules and insect material, respectively, suggesting they were able to feed more selectively throughout winter. Our study indicates that ice regimes in temperate rivers can affect organic-matter dynamics and feeding ecology of aquatic insects, a possibility that deserves additional investigation, particularly in light of potential changes to the ice regimes of rivers with changing climate."

Cain,DJ; Luoma,SN; Wallace,WG 2004 Linking metal bioaccumulation of aquatic insects to their distribution patterns in a mining-impacted river. Environmental Toxicology and Chemistry 23, 1463-1473. PDF
     Abstract: "Although the differential responses of stream taxa to metal exposure have been exploited for bioassessment and monitoring, the mechanisms affecting these responses are not well understood. In this study, the subcellular partitioning of metals in operationally defined metal-sensitive and detoxified fractions were analyzed in five insect taxa. Samples were collected in two separate years along an extensive metal contamination gradient in the Clark Fork River (MT, USA) to determine if interspecific differences in the metal concentrations of metal-sensitive fractions and detoxified fractions were linked to the differences in distributions of taxa relative to the gradient. Most of the Cd, Cu, and Zn body burdens were internalized and potentially biologically active in all taxa, although all taxa appeared to detoxify metals (e.g., metal bound to cytosolic metal-binding proteins). Metal concentrations associated with metal-sensitive fractions were highest in the mayflies Epeorus albertae and Serratella tibialis, which were rare or absent from the most contaminated sites but occurred at less contaminated sites. Relatively low concentrations of Cu were common to the tolerant taxa Hydropsyche spp. and Baetis spp., which were widely distributed and dominant in the most contaminated sections of the river. This suggested that distributions of taxa along the contamination gradient were more closely related to the bioaccumulation of Cu than of other metals. Metal bioaccumulation did not appear to explain the spatial distribution of the caddisfly Arctopsyche grandis, considered to be a bioindicator of metal effects in the river. Thus, in this system the presence/absence of most of these taxa from sites where metal exposure was elevated could be differentiated on the basis of differences in metal bioaccumulation."

Cuffney,TF and Minshall,GW 1981 Life history and bionomics of Arctopsyche grandis (Trichoptera) in a central Idaho stream. Holarctic Ecology 4(4) 252-262. first page on JSTOR
     Abstract: " Arctopsyche grandis was studied for two years in a cold stream in central Idaho. Larvae have a one year life cycle consisting of five instars. Three to four instars are present in most months. Growth is rapid in summer with instar I and II passing to IV and V in 30 d or less. Little or no growth occurs during winter. Maximum larval densities were 547 (1977) and 2060 m-2 (1978) of planar rock surface area. Populations fitted a negative exponential survivorship curve with similar exponents (-0.0078, -0.0103) in both years. Larval growth was generally isometric with head capsule width (403-2197 μm) and weight (0.05-16.23 mg AFDW) increasing by a factor of 1.5 between instars. Net dimensions correlated with head capsule width and nets were made by all instars and maintained throughout the year. Larvae fed preferentially on animals and diatoms avoiding vascular plant detritus. No differences were detected in diet among the instars."

Cushman,RM 2014 Biogeography of the caddisfly genus Arctopsyche McLachlan, 1868 (Trichoptera: Hydropsychidae) in North America. Pan-Pacific Entomologist, 90(4).
     Abstract: " This paper summarizes the distribution of the four species of the caddisfly genus Arctopsyche McLachlan, 1868 in North America and describes natural and man-induced factors that could account for that distribution. It proposes some possible future scenarios of speciation, local extirpation, or extinction."

DeJong,GD 2002 Variation in abdominal sa2 and sa3 setation in larvae of Arctopsyche grandis (Banks) (Trichoptera: Hydropsychidae). Proceedings of the Entomological Society of Washington 104:242-243.
     Some of the variation measured by the author may have been due to the presence of A. inermis larvae mixed with A. grandis larvae.

DeWalt,RE; Stewart,KW; Moulton,SR and Kennedy,JH 1994 Summer emergence of mayflies, stoneflies, and caddisflies from a Colorado mountain stream. Southwestern Naturalist 39 (3) 249-256.

Djernæs,M and Sperling,FAH 2012 Exploring a key synapomorphy: correlations between structure and function in the sternum V glands of Trichoptera and Lepidoptera (Insecta). Biological Journal of the Linnean Society, 106: 561-579.
     Quote from page 28: "A thumb-shaped protuberance is found in Stenopsychodes mjoebergi (Stenopsychidae) (Figure 2-2 A) and Arctopsyche grandis (Hydropsychidae: Arctopsychinae) (Figures 2-6 A, B; 2-19 B). A smaller protuberance is found in Parapsyche elsis (Hydropsychidae: Arctopsychinae) (Figure 2-19 C). "

Givens,DR and Ruiter,DE 2015 Clarification of the taxonomic status and distribution of Arctopsyche inermis Banks, 1943 and Arctopsyche ladogensis (Kolenati, 1859) (Trichoptera: Hydropsychidae: Arctopsychinae). The Pan-Pacific Entomologist, 91(2) 192-195. Full Text
     They found that Arctopsyche inermis is different after all from Arctopsyche grandis and describe the male genitalia to prove it. These species are sympatric which means they live in the same habitat. It is possible that our two color morphs of larval A. grandis seen in the upper East River drainage of Gunnison County are these two species.
Quote from page 192: "The shape of the male tergum X will separate A. inermis from A. grandis (Schmid, 1968). An examination of 81 males of A. inermis and 214 males of A. grandis indicates there is consistency in the structure of tergum X of the male. In all the males examined, tergum X in A. inermis narrows gradually to a very long, slender point and those of A. grandis, while narrowing to a point, do so abruptly, never as a long, slender tapered apex (Schmid, 1968). Also the basal area of tergum X is thicker in A. inermis than A. grandis, evident in both the dorsal and lateral aspect. "

Givens,DR and Smith,SD 1980 A synopsis of western Arctopsychinae (Trichoptera: Hydropsychidae). Melanderia 35:1-24.

Hauer,RF and Stanford,JA 1981 Larval specialization and phenotypic variation in Arctopsyche grandis (Trichoptera: Hydrospsychidae). Ecology 62(3)645-653. Abstract PDF

Hauer,FR; Stanford,JA and Ward,JV 1989 Serial discontinuities in a Rocky mountain river. II. Distribution and abundance of trichoptera. Regulated Rivers: Research and Management 3(1) 177-182.
     Abstract: "River regulation in the headwaters and middle reaches of the Gunnison River, Colorado, significantly altered distributions and abundances of Trichoptera fauna. Twenty-five species were collected from mainstream samples, with the greatest species richness occurring at an unregulated, rhithron segment above the central reach dams. At sites immediately below the three hypolimnial-release dams and a reregulation dam, species richness was reduced 35-90 per cent and abundance > 95 per cent. Net-spinning caddisflies were the dominant trichopterans at unregulated sites; Arctopsyche grandis in the upper reaches (218 organisms, 586 mg dry mass m-2) and Hydropsyche cockerelli, H. occidentalis and Cheumatopsyche pettiti in the lower river (9041 total organisms, 6621 mg m-2), downstream from the last dam. The observed distributional pattern of low trichopteran densities in dam tailwaters and high hydropsychid densities at sites 60-80 km below the central reach dams is a classic expression of continuum resets and adjustments in response to stream regulation as predicted by the Serial Discontinuity Concept. "

Herrmann,SJ; Ruiter,DE and Unzicker,JD 1986 Distribution and records of Colorado Trichoptera. Southwestern Naturalist 31 (4) 421-457.
     They note the habitat for this species is streams and rivers, the altitudinal range is 1913m to 3036m and adult collection dates are 10 May to 10 October. Quote from page 427: "This large hydropsychid is widespread and easily collected with an ultraviolet light." They list this species as present in Gunnison county.

Jannot,JE and Kerans,BL 2003 Body size, sexual size dimorphism, and Rensch's rule in adult Hydropsychid caddisflies (Trichoptera: Hydropsychidae). Canadian Journal of Zoology 81, 1956-1964.
     As part of their investigations, the authors measured 20 museum specimens of Arctopsyche grandis preserved in ethanol finding that adult males were 9.63 ± 0.24 mm in length and females were 12.55 ± 0.22 mm in length. They measured length from the center of the head between the eyes to the posterior margin of the 8th segment. Their data also indicates the subfamily Arctopsychinae contains on average the largest insects in the family Hydropsychidae. More details

Kashian,DR; Prusha,BA and Clements,WH 2004 Influence of total organic carbon and UV-B radiation on zinc toxicity and bioaccumulation in aquatic communities. Environmental Science & Technology. 38(23):6371-6376.
     Abstract: "The effects of total organic carbon (TOC) and UV-B radiation on Zn toxicity and bioaccumulation in a Rocky Mountain stream community were assessed in a 10-d microcosm experiment. We predicted that TOC would mitigate Zn [zinc] toxicity and that the combined effects of Zn and UV-B would be greater than Zn alone. However, TOC did not mitigate Zn toxicity in this study. In fact, treatments with TOC plus Zn had significantly lower community respiration as compared with the controls and Zn concentrations associated with the periphyton increased in the presence of TOC. UV-B had no additive effect on periphyton Zn accumulation or community respiration. Heptageniid mayflies (Ephemeroptera) were particularly sensitive to Zn, and reduced abundances were observed in all Zn treatments. UV-B did not additionally impact Heptageniid abundances; however UV-B did have a greater effect on macroinvertebrate drift than Zn alone. Ephemeroptera, Plecoptera, and Trichoptera (groups typically classified as sensitive to disturbance) were found in highest numbers in the drift of UV-B + Zn treatments. Measures of Zn accumulation in the caddisfly Arctopsyche grandis, periphyton biomass, and total macroinvertebrate abundance were not sufficiently sensitive to differentiate effects of TOC, UV-B, and Zn. These results indicate that UV-B and TOC affect Zn bioavailability and toxicity by impacting species abundance, behavior, and ecosystem processes. "

Kiffney,PM and Clements,WH 1993 Bioaccumulation of heavy metals by benthic invertebrates at the Arkansas River, Colorado. Environmental Toxicology and Chemistry 12, 1507-1517.
     Quote from page 1512: "Variation among taxa: Metal concentrations in organisms collected from station AR-5 [impacted by heavy metal pollution from California Gulch] (fall, spring, summer) varied significantly among taxa (Fig 7). The highest concentrations were generally found in the mayfly Baetis spp., the stonefly Pteronarcella badia, and the caddisfly A. grandis, whereas the lowest levels were measured in the two predators, Skwala americana, and Rhyacophila spp."

Lowe,WH and Hauer,FR 1999 Ecology of two large, net-spinning caddisfly species in a mountain stream: distribution, abundance, and metabolic response to a thermal gradient. Can. J. Zool./Rev. can. zool. 77(10): 1637-1644. Abstract

Mecom,JO 1972a Feeding habits of Trichoptera in a mountain stream. Oikos 23: 401-407. Abstract and first page
     Abstract: " The gut contents of more than 900 Trichoptera larvae from the St. Vrain River of Colorado were determined by Millipore filter analysis. They ingested a mixed diet of detritus, vascular plants, diatoms and other algae (e.g. Ulothrix). Vascular plant fragments, detritus, and filamentous algae were the major food categories ingested from late spring through early summer, while diatoms were most commonly consumed in mid-winter and early spring. Seasonal dietary changes were apparently related to general availability of organic material and larval microhabitat. Hydropsyche sp., Arctopsyche grandis, Hydropsyche occidentalis and Brachycentrus americanus were predatory or cannibalistic during a brief period from May to August. This carnivorous behavior was not directly correlated either to species crowding or population developmental changes. "

Mecom,JO 1972 Productivity and distribution of Trichoptera larvae in a Colorado mountain stream. Hydrobiologia 40(2): 151 - 176. Abstract

Milne,LJ and Milne,MJ 1938. The Arctopsychidae of continental America north of Mexico (Trichoptera). Bulletin of the Brooklin Entomological Society 33:97-110.

Nimmo,AP 1987 The adult Arctopsyche and Hydropsyche (Trichoptera) of Canada and adjacent United States. Questiones Entomologicae 23:1-189.

Peckarsky,BL 1980 Influence of detritus on colonization of stream invertebrates. Canadian Journal of Fisheries and Aquatic Sciences 37, 957-963.

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.

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

Prusha,BA and Clements,WH 2004 Landscape attributes, dissolved organic C, and metal bioaccumulation in aquatic macroinvertebrates (Arkansas River Basin, Colorado). Journal of the North American Benthological Society 23 (2) 327-339.
     Abstract: " Relationships among landscape attributes, instream dissolved organic C (DOC) concentrations, and metal bioaccumulation in Arctopsyche grandis and Drunella doddsi were investigated in the Upper Arkansas River Basin, Colorado. A Geographic Information System (GIS) was used to calculate landscape attributes in 16 watersheds where DOC concentrations were measured from May to August 2001. Metal concentrations in Arctopsyche and Drunella were related to physicochemical characteristics measured in these streams and in the Arkansas River. Results of multiple linear regression showed that % forested area explained 47% and 59% of the variation in maximum and mean DOC concentrations, respectively. Maximum DOC was negatively associated with the concentration of Zn (R2 = 0.25) and Cd (R2 = 0.39) in Arctopsyche. DOC concentration did not describe metal concentrations in Drunella, which accumulated significantly more Zn, Cd, and Cu than Arctopsyche. The higher metal concentrations and the absence of a DOC effect on metal uptake in Drunella most likely resulted from dietary exposure to metal-enriched detritus and periphyton. Our results indicate that % forested area within a watershed can be used to describe DOC concentrations, which in turn influence metal bioaccumulation in Arctopsyche. To our knowledge, this study is the first to quantify the relationship between landscape attributes and DOC, and to demonstrate the influence of DOC on metal bioaccumulation in benthic macroinvertebrates in the field."

Rader,RB and Ward,JV 1988 Influence of regulation on environmental conditions and the macroinvertebrate community in the upper Colorado River. Regulated Rivers: Research and Management 2:597-618.
     Quote from page 611: "The reference site was represented by twelve species of caddisflies, including relatively abundant populations of Arctopsyche grandis and Rhyacophila acropedes. Trichopterans at the regulated site, however, were represented by nine rare and three slightly more abundant caddisflies (Hydroptila sp., Brachycentrus americanus, and Hesperophylax designatus). The abundance of net-spinning caddisflies was significantly reduced in the regulated site compared to both reference and recovery locations (p=0.05), as has been reported by several workers (Armitage and Capper, 1976; Müller, 1962; Ward, 1987). "

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

Schmid,F 1968 La famille des Arctopsychides (Trichoptera). Memoirs of the Entomological Society of Quebec 1:4-84.
      Givens and Ruiter (2015) noticed these figures are reversed.

Schmidt,TS; Clements,WH; Zuellig,RE; Mitchell,KA; Church,SE; Wanty,RB, ... and Lamothe,PJ 2011 Critical tissue residue approach linking accumulated metals in aquatic insects to population and community-level effects. Environmental science and Technology, 45(16) 7004-7010. PDF
     Abstract: "Whole body Zn concentrations in individuals (n = 825) from three aquatic insect taxa (mayflies Rhithrogena spp. and Drunella spp. and the caddisfly Arctopsyche grandis) were used to predict effects on populations and communities (n = 149 samples). Both mayflies accumulated significantly more Zn than the caddisfly. The presence/absence of Drunella spp. most reliably distinguished sites with low and high Zn concentrations; however, population densities of mayflies were more sensitive to increases in accumulated Zn. Critical tissue residues (634 μg/g Zn for Drunella spp. and 267 μg/g Zn for Rhithrogena spp.) caused a 20% reduction in maximum (90th quantile) mayfly densities. These critical tissue residues were associated with exposure to 7.0 and 3.9 μg/L dissolved Zn for Drunella spp. and Rhithrogena spp., respectively. A threshold in a measure of taxonomic completeness (observed/expected) was observed at 5.4 μg/L dissolved Zn. Dissolved Zn concentrations associated with critical tissue residues in mayflies were also associated with adverse effects in the aquatic community as a whole. These effects on populations and communities occurred at Zn concentrations below the U.S. EPA hardness-adjusted continuous chronic criterion."

Smith,SD 1968 The Arctopsychinae of Idaho. Pan-Pacific Entomologist 44, 102-112.
     Contains the first description of the larvae of Arctopsyche grandis. Also describes the difference in genitalia between male A. inermis and A. grandis. In spite of this, the author synonymizes A. inermis and A. grandis. Givens and Ruiter, 2015

The United States Geological Survey (USGS) National Water Quality Assessment Data Warehouse (NAWQA) shows this species is present in Gunnison County. Data as of 1Sep2005

Voelz,NJ and Ward,JV 1996a Microdistributions, food resources and feeding habits of filter-feeding Trichoptera in the Upper Colorado River. Archiv fur Hydrobiologie 137 (3) 325-348. PDF

Voelz,NJ and Ward,JV 1996b Microdistributions of filter-feeding caddisflies (Insecta: Trichoptera) in a regulated Rocky Mountain river. Canadian Journal of Zoology 74, 654-666. PDF

Wallace, JB 1975 The larval retreat and food of Arctopsyche; with phylogenetic notes on feeding adaptations in Hydropsychidae larvae (Trichoptera). Annals of the Entomological Society of America 68(1) 167-173. PDF
     Abstract: "Arctopsyche larvae generally construct somewhat cornucopia-shaped dwellings at the top and sides of large rocks in swift mountain streams and spin a capture net across a U-shaped frame at the anterior end of the larval abode. There is an increase in net mesh size in successive larval instars. The individual meshes of mature larval capture nets are the largest found to date in the Hydropsychidae. Based on larval foregut contents, 2nd instars are about 50% plant detritivores and 50% predators. In the last 2 instars foregut contents consisted of ca. 90% insect fragments and 10% plant material. The structure of the nets and larval abodes supports the placement of the Arctopsychinae as primitive Hydropsychidae. In the evolution of hydropsychid larvae there is a tendency toward more complicated larval feeding structures and smaller capture net mesh sizes."

Ward,JV; Kondratieff,BC and Zuellig,RE 2002 An Illustrated Guide to the Mountain Stream Insects of Colorado. 2nd ed. University Press of Colorado, Boulder, Colorado. 219 pages.
     Figure 78 from this book of an Arctopsyche grandis larvae

Brown,WS 2004 Trichoptera of Gunnison County, Colorado, USA