Caddisflies: Denning’s Agapetus caddisfly
(Trichoptera: Glossosomatidae: Agapetinae) Profile prepared by Sarah Foltz, The Xerces Society for Invertebrate Conservation
Endemic to Oregon, Agapetus denningi is known definitively only from the type locality; Rogue River National Forest, Oregon, where it was collected prior to 1951. Its global status is GH: Possibly Extinct. Habitat information from the type locality is not known, but the closely related A. taho is common in mid-order streams of moderate gradient in forested areas over a wide elevation range. These streams often have an open mixed deciduous-coniferous canopy, with substrates dominated by cobble-boulder-bedrock that are free of fine sediment. Like other cold-water stream inhabiting caddisflies, habitat disturbance is probably the greatest immediate threat to this species. 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.
Adult: The adults of this species are dark brown in color, with slightly lighter legs and abdomen. Male length is 5 mm (0.2 in.). For an illustration of the genitalia, see Ross (1951). The following traits distinguish this species: Ninth segment nearly annular, with anterior margin evenly bowed. Tenth tergite with lobes bladelike and thin, each with lateral aspect fairly shallow, triangular, elongate, and ending in a sclerotized portion which is curved ventrad and beaklike. Cercus moderately long and slender, with an irregular row of long setae. Clasper with base massive, apex tapering to a point curved sharply mesad; at the dorsal apex of the basal portion is a short sharp projection pointed mesad. Aedeagus with simple rods. Female: Size, color, and general structure similar to male. Female characters typical for ophionis complex, for which means of specific separation in this sex are not yet known (Ross 1951). This species is apparently closely related to A. taho, but differs in that A. denningi has a more triangular lateral aspect of the clasper and an almost even dorsal outline of the tenth tergite, which ends in a simple downcurved point (Ross 1951). Wisseman (2008, pers. comm.) suggests re-examining the original material for confirmation of the identification.
Immature: Although the immature stages of this species are unknown, the larvae of this family build distinctive, tortoise shell-shaped cases out of rock fragments. The case is flat on the bottom and the underside is open except for a small “strap” of rocks or sand, which holds the larva or pupa in place.
Endemic to Oregon. Known definitively only from the type locality; Rogue River National Forest, Oregon. The type collection was made prior to 1951, and most of the collection data for this record is unknown (e.g., date, county, location, habitat, collector, determiner, life-stages). Wisseman (2008, pers. comm.) maintains an additional record for one male pupae of this species from Douglas County, Umpqua National Forest, Castle Rock Creek, 1999. Due to differences between the male genitalia and the original diagrams, however, this record should be considered tentative until an additional series is collected from the site, and/or comparisons are made with the type specimen (Wisseman 2008, pers. comm.).
Inventory: Focus initial survey efforts on Castle Rock Creek in the Umpqua National Forest and on mid- to large streams in the Rogue River National Forest. Since the larvae of this species are unknown, collect and rear out as many life stages as possible, in order to associate immature stages with adults (see Survey Protocol, attached). Further documentation of this species’ range and habitat is especially critical for advancing understanding of its status and needs and taking the appropriate conservation measures.
Management: Protect all new and known sites and their associated watersheds from practices that would adversely affect any aspect of this species’ life cycle. Riparian habitat protection, including maintenance of water quality, substrate conditions, and canopy cover, would likely benefit and help maintain this species.
Research: Basic research of the habitat, range, life-history, and abundance of this species is needed.
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.
NatureServe. 2008. “Agapetus denningi.” NatureServe Explorer: An online encyclopedia of life [web application]. Feb. 2008. Version 7.0. NatureServe, Arlington, Virginia. 6 Oct. 2008 .
Ross, H.H. 1951. Phylogeny and biogeography of the caddisflies of the genera Agapetus and Electragapetus (Trichoptera; Rhyacophilidae). Journal of the Washington Academy of Science 41: 347-356.
Wiggins, G.B. 1996. Larvae of the North American Caddisfly Genera (Trichoptera). Second Edition. Toronto and Buffalo: University of Toronto Press, 457pp.
Wiggins, G.B. 2004. Caddisflies: the underwater architects. University of Toronto Press, Toronto. 292pp.
Wisseman, Robert W. 2005. Personal communication with Eric Scheuering.
Wisseman, Robert W. 2008. Personal communication with Sarah Foltz.