LIFE-HISTORY, GROWTH, SURVIVORSHIP, AND PRODUCTION OF HYDROPSYCHE-SLOSSONAE IN MILL-CREEK, VIRGINIA

We describe life history and production of Hydropsyche slossonae Banks in Mill Creek, Virginia, a first-order stream in the Central Appalachian Ridges and Valleys ecoregion. Each adult female laid approximately 230 eggs which hatched in 13 d. Five larval instars were recorded with most individuals overwintering in instars III and IV. Pupation and emergence occurred primarily over a 6-wk period in May and June. No mortality in the egg stage was detected, while high mortality in instar I (92.9%) was due partly to sibling cannibalism. Instars II-V showed constant low mortality, with high mortality again in the pupal stage; 0.5% of the original eggs survived to adulthood. Growth analysis revealed two distinct growth phases: one from hatching through instar IV (0.007 mg/d) and a much faster growth rate for instar V in May (0.148 mg/d). Production estimates for the entire generation ranged from approximately 3 to 5 g/m2 and were highly variable. On a per-day basis, production occurred at specific times of the year. Yield per day peaked slightly later than peaks in production. High daily production occurred immediately after hatching as a result of 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. It may be more accurate to estimate production by predicting biomass from survivorship and growth functions than directly from sample data.