Archaic black flies and ancient forests: Conservation of Parasimulium habitats in the Pacific Northwest

1. Parasimulium (Diptera: Simuliidae) is one of the most distinctive, enigmatic and poorly collected groups of black flies in North America. The genus is confined to streams in the mesic coniferous forests of the Pacific Northwest, from southern British Columbia to northern California. 2. The immature stages of these unusual flies are specialized for life in the hyporheic zone, a region of flowing water beneath and lateral to the stream bed. Parasimulium shares this habitat with a diverse assemblage of subterranean aquatic invertebrates. 3. Most Parasimulium research has been conducted in the Cascade Range of Oregon, particularly streams in the Columbia River Gorge. Collection records suggest a correlation between the distribution of some species of Parasimulium and that of ancient forests in the Pacific Northwest. However, definitive evidence that Parasimulium is an ecologically sensitive ‘indicator’ species awaits additional observations on the group's distribution and habitat requirements. 4. This paper discusses the potential role of aquatic invertebrates in studies of ancient forests, and concludes that it may be especially great for hyporheic species, which typically inhabit zones of marked environmental stability. Data on these and other ecologically sensitive taxa will provide valuable insights into the management and conservation of surface and groundwater habitats of the Pacific Northwest.