Caddisflies: Green Springs Mountain Farulan caddisfly
(Trichoptera: Uenoidae: Uenoinae) Profile prepared by Sarah Foltz, The Xerces Society for Invertebrate Conservation
This rare, possibly extinct species is known only from two males collected in the fall of 1950 at Green Springs Mountain, Jackson Co., Oregon. Subsequent targeted searches at the type locality by R. Wisseman in the 1990’s did not yield specimens, nor was very suitable habitat found. Farula species generally require cold-water stream habitat, yet all of the encountered streams heated up substantially in the summer, and many were seasonal or intermittent. The loss of trees through timber harvest poses threats to this species, since it occupies forested habitats, and trees provide shade that maintains appropriate water levels and temperatures for larval and pupal development. Continued global climate change may further threaten the long-term survival of this cold-water species.
Adult: The description of this species is based on two males collected at one location (the type series and only known specimens). The adult head and thorax are testaceous, the appendages yellowish, and the wings uniformly ferruginous. Length of males: 5 mm (0.2 in.). Details concerning wing venation, palpi, and antennae are obscure, due to poor condition of specimens. The adult genitalia are as follows: Process (probably the tenth tergite) from lateral aspect sinuate, its apex slender and acute, from dorsal aspect the apex gradually curved laterad; lateral margin about midway bearing a prominent, acute, lateral structure with distal margin darkened and heavily sclerotized. Cercus, slender and elongate. Claspers, acuminate as seen from lateral aspect; from ventral aspect slender, elongate, connected at base by a narrow to an acute, slender point, mesal margin straight. Aedeagus, emarginate apically, gradually tapering toward base, trough-like (Denning 1958). Species identification is based on the following diagnostic characters of the genitalia: Inferior appendages with basal segment comprising only one elongate sclerotized process, the lateral spiniform process lacking with a slender but clavate second segment arising from the base of the first. External branch of segment ten approximately as long as inferior branch (Wiggins et. al. 1985).
Larva: The immature stages of this species are unknown, but larvae of the genus Farula make extremely slender portable cases, lack abdominal gills, and their sclerotized parts are mostly uniform dark brown or black (Wiggins 1996). The smoothly textured cases, so slender they could be mistaken for pine-needles (Wiggins 1996), are constructed of small sand grains fitted closely together and covered externally and internally with a thin silken lining (Wiggins 1996, Merritt et al. 2008). Cases can be up to 14.5 mm (0.6 in.) in length. Farula is further distinguished from other genera in the Uenoidae family by the following characters: pronotum broadest anteriorly in dorsal aspect, mesonotal sclerites with anterior margin rounded and single median notch between two sclerites, pronotum with anterior margin and anterolateral corner curved, darkened posterolateral corner of each mesonotal sclerite not reaching the mid-lateral point of sclerite, abdomen with filaments of lateral fringe scattered and arising over less than half of most segments, but with prominent and discrete tuft of filaments at anterior edge of segment II (Wiggins 1996).
Pupa: Cases in this genus are converted into pupal chambers by a silken sieve membrane spun across the inside posterior opening (Wiggins 1996).
Endemic to Oregon. Known only from a collection of two males in the fall of 1950 from Green Springs Mountain, Jackson Co., Oregon, 16 to 19.3 km (10 – 12 miles) east of Ashland (Anderson 1976, but note that the collection year provided in this reference (1960) is a misprint). Subsequent targeted searches at Green Springs Mountain by R. Wisseman in the 1990’s did not yield specimens, nor was very suitable habitat found. Farula species generally require cold-water, yet all of the encountered streams heated up substantially in the summer, and many were seasonal or intermittent (Wisseman 2008, pers. comm.).
Federal Land: The only known documented occurrence is from the Medford District, BLM.
Most trichopteran species have highly specific preferences with regard to water temperature, velocity, dissolved-oxygen levels, and substrate characteristics, and are therefore sensitive to a wide array of habitat alterations. Increased sedimentation, eutrophication, and chemical pollution by grazing, development, and agriculture in the watershed could harm this species. The loss of trees through timber harvest poses additional threats, since this species occupies forested habitats, and trees provide shade that maintains appropriate water levels and temperatures for larval and pupal development.
Continued global climate change may further threaten the long-term survival of this cold-water species. Projected changes due to this factor include increased frequency and severity of seasonal droughts and flooding, reduced snowpack to feed river flow, increased siltation, and increased air and water temperatures (Field et al. 2007), all of which could impact this species and its habitat unfavorably. Recent surveys at the type locality found only unsuitable habitat for this species: all of the encountered streams heated up substantially in the summer, and many were seasonal or intermittent (Wisseman 2008, pers. comm.).
Inventory: Conduct further surveys at and around the type locality to help establish the current status of this rare species. Explore similar mountainous areas in the region for suitable habitat, and survey for this species.
Management: Protect all new sites and their associated watersheds from timber harvest and other practices that would adversely affect any aspect of this species’ life cycle. Undisturbed buffers of coniferous forest around stream habitat may be critical for the survival of species within the Farula genus (Applegarth 1995). Riparian habitat protection, including maintenance of water quality, substrate conditions, and canopy cover, would likely benefit and help maintain this species.
Anderson, N.H. 1976. The distribution and biology of the Oregon Trichoptera. Oregon Agricultural Experiment Station Technical Bulletin, 134:1-152.
Applegarth, J.S. 1995. Invertebrates of special status or special concern in the Eugene district. U.S. Department of the Interior, Bureau of Land Management. Eugene, OR. 126 pp.
Denning, D.G. 1958. The genus Farula (Trichoptera: Limnephilidae). Annals of the Entomological Society of America 51: 531-535.
Field, C.B., Mortsch, L.D., Brklacich, M., Forbes, D.L., Kovacs, P., Patz, J.A., Running, S.W. and M.J. Scott. 2007. Chapter 14: North America. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Parry, M.L., Canziani, O.F., Palutikof, J.P., van der Linden, P.J. and Hanson, C.E., eds.). Cambridge University Press, Cambridge, UK. Available at: www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter14.pdf.
Merritt, R.W., Cummins, K.W., and M.B. Berg. 2008. An introduction to the aquatic insects of North America. Fourth Edition. Kendall/Hunt Publishing Co., Dubuque, Iowa. 1158pp.
NatureServe. 2008. “Farula davisi.” NatureServe Explorer: An online encyclopedia of life [web application]. Feb. 2008. Version 7.0. NatureServe, Arlington, Virginia. 21 Oct. 2008
Wiggins, G.B., J.S. Weaver III, and J.D. Unzicker. 1985. Revision of the caddisfly family Uenoidae (Trichoptera). Canadian Entomologist 117: 763-800.
Wiggens, G.B. 1996. Larvae of the North American Caddisfly Genera (Trichoptera). Second Edition. Toronto and Buffalo: University of Toronto Press, 457pp.
Wisseman, Robert W. 2008. Personal communication with Sarah Foltz.