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Trichoptera: Limnephilidae of Gunnison County, Colorado

Limnephilus externus

(Hagen) 1861
Updated 27 July 2017
TSN 116146
Limnephilus externus caddisfly out of its case


Ponds and lakes in the Northern East River Valley


Distinctive case of transversely crossing Carex or other aquatic plants. Case structure varies from big fluffy cases with distinctly green leaf stems at the higher elevations of Gunnison County to more tightly wound cases at the Kettle ponds south of Gothic. Case structure varies by available plants, prescence/abscence of predators and the density of other L. externus. When food supplies are low, they chew each others cases down.

Locations Collected

Kettle Ponds, Mexican Cut Nature Preserve, Meridian or Long Lake, Snodgrass Ponds Stampede, Horse and Foal, 401 Beaver Ponds, South of Gunnison? Limnephilus externus caddisfly inside its case

Good Links

On this website:
Limnephilidae Introduction

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.


Berte,SB; Pritchard,G 1983 The structure and hydration dynamics of Trichopteran (Insecta) egg masses. Canadian Journal of Zoology 61, 378-384.

Berte,SB; Pritchard,G 1986 The life histories of Limnephilus externus (Hagen), Anabolia bimaculata (walker), and Nemotaulius hostilis (Hagen) (Trichoptera:Limnephilidae) in a pond in southern Alberta, Canada. Canadian Journal of Zoology 64, 2348-2356.

Czachorowski,S 1997 Limnephilus externus Hagen (Trichoptera: Limnephilidae) in Poland. Polskie Pismo Entomologiczne 66: 117-119.

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.

Hagen,HA 1861 Synopsis of the Neuroptera of North America with a list of South American species. Smithsonian Miscellaneous Collections 4, 1-344.
     Described as Limnophilus externus. Hagen's Glossary (pdf)

Hagen's description of the caddisfly Limnephilus externus

Herrmann,SJ; Ruiter,DE and Unzicker,JD 1986 Distribution and records of Colorado Trichoptera. Southwestern Naturalist 31 4, 421-457.
     The authors show this species present in Gunnison County.

Jannot,JE; Wissinger,SA and Lucas,JR 2008 Diet and a developmental time constraint alter life-history trade-offs in a caddis fly (Trichoptera: Limnephilidae). Biological Journal of the Linnean Society, 95(3), 495-504. Abstract   PDF

McCullagh,BS; Wissinger,SA and Marcus,JM 2015 Identifying PCR primers to facilitate molecular phylogenetics in Caddisflies (Trichoptera). Zoological Systematics, 40(4) 459 PDF

Nimmo, A 1971 The adult Rhyacophilidae and Limnephilidae (Trichoptera) of Alberta and eastern British Columbia and their post glacial origin. Quaestiones Entomologicae 73: 3-234.

Pritchard,G and Berté,SB.1987 Growth and food choice by two species of limnephilid caddis larvae given natural and artiflcial foods. Freshwater Biology, 18(3), pp.529-535.
     Summary: " 1. Larvae of the caddisfly Limnephilus externus grew faster than those of Nemotaulius hostilis in a permanent pond in southern Alberta.
2. We investigated whether this was due to more efficient food processing by L. externus, whether their growth coincided with high environmental temperatures, or whether they had the ability to choose and exploit higher quality food.
3. Of five foods used, protein content was highest in wheat flakes, similar in alder, bur-reed and willow leaves, and lowest in the moss Leptodictyum.
4. Both species grew faster and survived better on the wheat flakes, but there was no statistically significant difference between species on the same food when reared at 4 or 8°C in the laboratory.
5. At 16°C L. externus grew better than N. hostilis when fed wheat, but N. hostilis survived better on alder. Both species had higher survival and growth rates per day-degree at 8 and 4 than at 16°C.
6. Thus, faster growth rates of L. externus in the field appear to be due simply to higher temperatures during the larval growth period. Indeed, N. hostilis had a significantly higher growth rate per day-degree in a field experiment.
7. In food preference experiments, L. externus chose wheat first, moss second, alder third, and willow last; N. hostilis chose alder first, bur-reed second, moss third, and wheat last.
8. Protein content, leaf texture, microbial conditioning, and an interaction between larval behaviours selecting for food quality and case materials, are potential factors that influence 'food preference' results."

Ruiter,DE 1995 The adult Limnephilus Leach (Trichoptera:Limnephilidae) of the new world. Vol. 11. Ohio Biological Survey, College of Biological Sciences, Ohio State University, Columbus, Ohio. 200 pages.
     Keys and illustrates the adults of this species. Also shows it is present in Gunnison County.

Wissinger, SA 2004 Population fluctuations in caddisflies inhabiting high-elevation wetlands in central Colorado . Presented at the NABS Annual meeting, Vancouver, British Columbia, in Population Ecology 2 Abstract

Wissinger,SA; Brown,WS and Jannot,JE 2003 Caddisfly life histories along permanence gradients in high altitude wetlands in Colorado (U.S.A.). Freshwater Biology 48(2). Abstract Pdf Icon (427 KB)
     " SUMMARY 1. Larvae of cased caddisflies (Limnephilidae and Phryganeidae) are among the most abundant and conspicuous invertebrates in northern wetlands. Although species replacements are often observed along permanence gradients, the underlying causal mechanisms are poorly understood. In this paper, we report on the distributional patterns of caddisflies in permanent and temporary high-altitude ponds, and how those patterns reflect differences in life history characteristics that affect desiccation tolerance (fundamental niches) versus constraints related to biotic interactions (realised niches).
2. Species (Hesperophylax occidentalis and Agrypnia deflata) that were encountered only in permanent ponds are restricted in distribution by life history (no ovarian diapause, aquatic oviposition, and/or inability to tolerate desiccation). Although the egg masses of H. occidentalis tolerate desiccation, the larvae leave the protective gelatinous matrix of the egg mass because adults oviposit in water.
3. Three species (Asynarchus nigriculus, Limnephilus externus and L. picturatus) have life history characteristics (rapid larval growth, ovarian diapause and terrestrial oviposition of desiccation-tolerant eggs) that should facilitate the use of both permanent and temporary habitats. However, A. nigriculus is rare or absent in most permanent ponds, and L. externus and L. picturatus are rare or absent in most temporary ponds. Experimental data from a previous study on the combined effects of salamander predation and interspecific interactions among caddisflies (e.g. intraguild predation) suggest that biotic interactions limit each species to a subset of potentially exploitable habitats.
4. Many wetland invertebrates exhibit species replacements along permanence gradients, but few studies have separated the relative importance of the effects of drying per se from the effects of biotic interactions. Our results emphasise the complementary roles of comparative data on life histories and experimental data on competition and predation for understanding invertebrate distributions along permanence gradients."

Wissinger,SA and Eldermire,C and Whissel,JC 2005 The role of larval cases in reducing aggression and cannibalism among caddisflies in temporary wetlands. Wetlands 24(4) 777-783. Abstract

Wissinger,SA; Sparks,GB; Rouse,GL; Brown,WS; Steltzer,HM 1996 Intraguild predation and cannibalism among larvae of detritivorus caddisflies in subalpine wetlands. Ecology 77 8, 2421-2430. PDF

Wissinger,SA; Whissel,J; Eldermire,C and Brown,W 1998. The role of caddis cases in deterring predators along a predator-permanence gradient in high-elevation wetlands. Bulletin of the North American Benthological Society 15(142 )

Wissinger,SA; Eldermire,C and Whissel,JC 2005 The role of larval cases in reducing aggression and cannibalism among caddisflies in temporary wetlands. Wetlands 24(4) 777-783. PDF
     Abstract: " Larvae of wetland caddisflies supplement their detrital diets with animal material. In some species this supplement is obtained by preying on other caddisflies. In this study, we conducted a series of laboratory experiments to a) compare intraspecific aggression and the propensity for cannibalism among six caddisfly species that occur along a gradient from vernal to autumnal to permanent high-elevation wetlands, and b) determine the importance of cases in preventing or reducing cannibalism and intraguild predation. We predicted that cannibalism and overall levels of aggression should be highest in species that occur in temporary habitats. We found that all of the species that use temporary habitats (Asynarchus nigriculus ,Hesperophylax occidentalis, Limnephilus externus, Limnephilus picturatus, Limnephilus secludens) were extremely aggressive towards and cannibalized conspecifics without cases. Species that typically occur in short-duration temporary wetlands were more aggressive than those in long-duration temporary wetlands. Cases prevented cannibalism in four of these temporary-habitat species, and reduced cannibalism among Asynarchus larvae. The latter species occurs in extremely ephemeral habitats where cannibalism provides a dietary supplement that probably facilitates emergence before drying. Asynarchus also preys on Limnephilus spp., and we found that cases dramatically reduced vulnerability to intraguild predation. Larvae of Agrypnia deflata, a species that occurs only in permanent wetlands, were least aggressive and rarely cannibalized conspecifics. Our results are consistent with the hypothesis that intraspecific aggression and the potential for cannibalism are highest in species that live in habitats with developmental time constraints. Many wetland invertebrates face developmental time constraints and selection for aggression in temporary habitats should be especially strong for taxa that rely on animal material to supplement a mainly detrital diet."

Wissinger,SA; Whissel,J; Eldermire,C and Brown,W 2006 Predator defense along a permanence gradient: roles of case structure, behavior, and developmental phenology in caddisflies, Oecologia, Pages 1 - 12. Abstract Pdf Icon (311 KB)

Wissinger,SA; Whiteman,HH; Sparks,GB; Rouse,GL and Brown,WS 1999 Foraging trade-offs along a predator-permanence gradient in subalpine wetlands. Ecology 80, 2102-2116. PDF
     Abstract: " We conducted a series of field and laboratory experiments to determine the direct and indirect effects of a top predator, the tiger salamander (Ambystoma tigrinum nebulosum), on larvae of two species of limnephilid caddisflies (Limnephilus externus and Asynarchus nigriculus) in subalpine wetlands in central Colorado. Asynarchus larvae predominate in temporary wetlands and are aggressive intraguild predators on Limnephilus larvae, which only predominate in permanent basins with salamanders. We first conducted a field experiment in mesocosms (cattle tanks) to quantify the predatory effects of different life stages of salamanders on the two caddisfly species. Two life stages of the salamanders (larvae and paedomorphs) preferentially preyed on Asynarchus relative to Limnephilus. Subsequent laboratory experiments revealed that high Asynarchus activity rates and relatively ineffective antipredatory behaviors led to higher salamander detection and attack rates compared to Limnephilus. In a second field experiment (full factorial for presence and absence of each of the three species), we found that salamander predation on Asynarchus had an indirect positive effect on Limnephilus: survival was higher in the presence of salamanders + Asynarchus than with just Asynarchus. In the laboratory we compared the predatory effects of salamanders with and without their mouths sewn shut and found the observed indirect positive effect on Limnephilus survival to be mainly the result of reduced numbers of Asynarchus rather than salamander-induced changes in Asynarchus behavior. We argue that indirect effects of predator-predator interactions on shared prey will be mainly density-mediated and not trait-mediated when one of the predators (in this case, Asynarchus) is under strong selection for rapid growth and therefore does not modify foraging behaviors in response to the other predator. The reciprocal dominance of Limnephilus and Asynarchus in habitats with and without salamanders probably reflects a trade-off between competitive superiority and vulnerability to predation. The high activity levels and aggressiveness that enable Asynarchus to complete development in temporary habitats result in strong asymmetric competition (via intraguild predation) with Limnephilus. In permanent habitats these same behaviors increase Asynarchus vulnerability to salamander predation, which indirectly benefits Limnephilus. This and previous work implicate salamanders as keystone predators that exert a major influence on the composition of benthic and planktonic assemblages in subalpine wetlands."

Notice the head and legs sticking out of the case to the left. There is a second caddis to the right who appears to be climbing into or chewing inside the back end of the first animal's case.

Brown,WS 2005 Trichoptera or Caddisflies of Gunnison County, Colorado