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Trichoptera: Hydropsychidae of Gunnison County, Colorado

Arctopsyche inermis
Great Grey Spotted Sedge

Banks, 1943

Created 7 January 2018
TSN 115537


These are relatively large and common invertebrates in a kick sample from the higher elevation streams of the Gunnison Basin. Gently overturning rocks in the stream allows you to see Arctopsyche larvae in their retreats sealed by nets made of silk.
We are not sure yet which of our larval color morphs are A. grandis vs A. inermis. Some animals have a white-striped head and some have a brown head without the stripe. Givens and Ruiter in 2015 found that A. grandis can be split back into A. grandis and A. inermis.

Good Links

On this website:
Introduction to the Hydropsychidae

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

Locations Collected

Possibly common in upper East River drainage and many other drainages in the Gunnison basin. Once we complete our rearing experiments, we'll know if our local larval color morphs correspond with the adults as described in Givens and Ruiter 2015.


Many of the references for Arctopsyche grandis may be discussing A. inermis as well.

Banks,N 1943 Notes and descriptions of Nearctic Trichoptera. Bulletin of the Museum of Comparative Zoology at Harvard College 92: 341-369, plates 1-6.
     Described as Arctopsyche inermis which was later synonymized with A. grandis.

Cushman,RM 2014 Biogeography of the caddisfly genus Arctopsyche McLachlan, 1868 (Trichoptera: Hydropsychidae) in North America. Pan-Pacific Entomologist, 90(4) 174-181.
     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."

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.

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

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."

"Do unto those downstream as you would have those upstream do unto you."  
Brown,WS 2018 Trichoptera of Gunnison County, Colorado, USA