Life history, survival, growth, and production of hydropsyche slossonae in Mill Creek, Virginia

Life history and annual production of Hydropsyche slossonae were determined in Mill Creek, Virginia, emphasizing aspects of its early life history. Mill Creek is a first—order stream in the Central Appalachian Ridges and Valleys ecoregion. Each adult female laid approximately 230 eggs in May and June which hatched in 13 days. Five larval instars were recorded with most individuals overwintering in III and IV instars. Pupation and emergence occurred primarily over a six week period in May and June. No mortality in the egg stage (0%) was detected, while high mortality in I instar (92.9%) was due in part to sibling cannibalism. Second through fifth instars showed constant, low mortality, with high mortality again in the pupal stage; an estimated 0.5% of the original eggs survived to adulthood. Growth analysis revealed two distinct growth phases; one from hatching through IV instar (0.008 mg/day) and a much faster growing V instar in May (0.085 mg/day).

Annual production estimates ranged from 3 to 5 g/m² and were highly variable. It may be more precise to estimate production by predicting biomass from survivorship and growth functions than directly from sample data. On a per day basis, production was not constant but varied during the year. Yield per day peaked slightly later than peaks in production. High daily production occurred immediately after hatching due to growth of many small individuals. At the end of the generation, there was another period of high daily production due to fast growth by fewer larger individuals. Most production occurred from March through June. At other times, daily production was relatively low.