Species profile: Rhyacophila dorsalis

March 14, 2014

Rhyacophila dorsalis (Curtis 1834)

Rhyacophila dorsalis is one of two members of the Family Rhyacophilidae found in Ireland (the other being Rhyacophila munda). This species can be found in stony, flowing waters of small streams to large rivers, with a substratum preference ranging from coarse gravel to boulders, and in high current velocities. Rhyacophila dorsalis has a preference for acid waters (pH < 7). It is a free-living species and so does not build a case like many other caddisfly larvae, feeding by active predation. In temperate latitudes, Rhyacophila dorsalis exhibits a univoltine reproductive pattern.

The larvae of Rhyacophila dorsalis can be readily identified, and separated from R. munda, based on a number of features. Both species lack hard, sclerotized plates on the 2nd & 3rd thoracic segments. Both species have tufted gills laterally on the abdominal segments, while R. dorsalis also has tufted gills on the thoracic segments compared to R. munda’s single filament thoracic gills. (The identification of R. dorsalis in Britain is complicated by the presence of Rhyacophila obliterata and Rhyacophila fasciata; species which have not been recorded in Ireland).

The larva is green in life, while preservation in 70% Industrial Methylated Spirits (IMS) renders it a pale pink-white colour.

Adults of Rhyacophila dorsalis can be found on the wing from April to October.

Records of Rhyacophila dorsalis on the National Biodiversity Data Centre mapping system can be found here.

References

Barnard, P. and Ross, E. (2012) The Adult Trichoptera (Caddisflies) of Britain and Ireland. RES Handbook Volume 1, Part 17.

Edington, J.M. and Hildrew, A.G. (1995) A Revised Key to the Caseless Caddis Larvae of the British Isles: with notes on their ecology. Freshwater Biological Association Special Publication No. 53.

Graf, W., Murphy, J., Dahl, J., Zamora-Muñoz, C. and López-Rodríguez, M.J. (2008) Distribution and Ecological Preferences of European Freshwater Species. Volume 1: Trichoptera. Astrid Schmidt-Kloiber & Daniel Hering (eds). Pensoft, Sofia-Moscow.

O’Connor, J.P. (2015) A Catalogue and Atlas of the Caddisflies (Trichoptera) of Ireland. Occasional Publication of the Irish Biogeographical Society, No. 11.

Last updated: 31/05/2016

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