Trichoptera: Limnephilidae of Gunnison County, Colorado
Limnephilus externus(Hagen 1861)
Updated 17 Apr 2020
HabitatPonds and lakes in the Northern East River Valley
DescriptionDistinctive 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 CollectedKettle Ponds, Mexican Cut Nature Preserve, Meridian or Long Lake, Snodgrass Ponds Stampede, Horse and Foal, 401 Beaver Ponds, South of Gunnison?
Good LinksOn this website:
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.
ReferencesBalik,JA; Taylor,BW; Washko,SE and Wissinger,SA 2018 High interspecific variation in nutrient excretion within a guild of closely related caddisfly species. Ecosphere, 9(5) p.e02205. PDF
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)
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 entire genus and particular species. Also shows it is present in Gunnison County COlorado.
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). (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. 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; 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
Abstract: " Comparative data from subalpine wetlands in Colorado indicate that larvae of the limnephilid caddisflies, Asynarchus nigriculus and Limnephilus externus, are reciprocally abundant among habitats-Limnephilus larvae dominate in permanent waters, whereas Asynarchus larvae dominate in temporary basins. The purpose of this paper is to report on field and laboratory experiments that link this pattern of abundance to biotic interactions among larvae. In the first field experiment, growth and survival were compared in single and mixed species treatments in littoral enclosures. Larvae, which eat mainly vascular plant detritus, grew at similar rates among treatments in both temporary and permanent habitats suggesting that exploitative competition is not important under natural food levels and caddisfly densities. However, the survival of Limnephilus larvae was reduced in the presence of Asynarchus larvae. Subsequent behavioral studies in laboratory arenas revealed that Asynarchus larvae are extremely aggressive predators on Limnephilus larvae. In a second field experiment we manipulated the relative sizes of larvae and found that Limnephilus larvae were preyed on only when Asynarchus larvae had the same size advantage observed in natural populations. Our data suggest that the dominance of Asynarchus larvae in temporary habitats is due to asymmetric intraguild predation (IGP) facilitated by a phenological head start in development. These data do not explain the dominance of Limnephilus larvae in permanent basins, which we show elsewhere to be an indirect effect of salamander predation. Behavioral observations also revealed that Asynarchus larvae are cannibalistic. In contrast to the IGP on Limnephilus larvae, Asynarchus cannibalism occurs among same-sized larvae and often involves the mobbing of one victim by several conspecifics. In a third field experiment, we found that Asynarchus cannibalism was not density-dependent and occurred even at low larval densities. We hypothesize that Asynarchus IGP and cannibalism provide a dietary supplement to detritus that may be necessary for the timely completion of development in these nutrient-poor, high-elevation wetlands."
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 (311 KB)
Abstract: "Species replacements along freshwater permanence gradients are well documented, but underlying mechanisms are poorly understood for most taxa. In subalpine wetlands in Colorado, the relative abundance of caddisfly larvae shifts from temporary to permanent basins. Predators on caddisflies also shift along this gradient; salamanders (Ambystoma tigrinum nebulosum) in permanent ponds are replaced by predaceous diving beetles (Dytiscus dauricus) in temporary habitats. We conducted laboratory and field experiments to determine the effectiveness of caddisfly cases in reducing vulnerability to these predators. We found that larvae of a temporary-habitat caddisfly (Asynarchus nigriculus) were the most vulnerable to salamanders. Two relatively invulnerable species (Limnephilus externus, L. picturatus) exhibited behaviors that reduced the likelihood of detection and attack, whereas the least vulnerable species (Agrypnia deflata) was frequently detected and attacked, but rarely captured because cases provided an effective refuge. Vulnerability to beetle predation was also affected by cases. The stout cases of L. externus larvae frequently deterred beetle larvae, whereas the tubular cases of the other species were relatively ineffective. Two of these vulnerable species (A. nigriculus and L. picturatus) often co-occur with beetles; thus, case construction alone is insufficient to explain patterns of caddisfly coexistence along the permanence gradient. One explanation for the coexistence of these two species with beetles is that they develop rapidly during early summer and pupate before beetle larvae become abundant. One species (L. picturatus) pupates by burying into soft substrates that serve as a refuge. The other (A. nigriculus) builds stone pupal cases, which in field experiments, more than doubles survival compared to organic pupal cases. The combined results of these experiments suggest that caddisfly distributions along permanence gradients depend on a suite of primary and secondary predator defenses that include larval and pupal case structure, predator-specific escape behaviors, and the phenology of larval development."
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