Life Cycle, Production and Survival Rates of Ptychoptera paludosa (Diptera: Ptychopteridae)

Life cycle, survival and production of the univoltine midge Ptychoptera paludosa whose larvae live in fine sandy sediments were studied in a German stream (1989-1990). Growth of the 4th larval instar was linear. Adults emerge from May, for ca 8 weeks ( 1985-1990); emergence was 0.56 g dry weight m^-2 lentic area (1990). Density decreased strongly only when larvae were young; except after an exceptional spate, numbers emerging were independent of discharge, Larval survival was ca 9%; only 10% of the potential offspring of the survivors actually appeared in the next generation. Secondary production (P) was 2.3 g ash free dry weight (AFDW) m^-2 y^-1, mean biomass (B) was 0.6 g AFDW m^-2, i.e., the P/B ratio was 3.8