Larvae and adults of Ancyronyx variegatus (Germar, 1824) were collected monthly from Elk Creek, Erie County, Pennsylvania, USA. Ancyronyx variegatus has a univoltine life cycle with six instars. Primary recruitment months were April, May, and June, and adults were present throughout the year. The annual secondary production of A. variegata in Elk Creek was 0.55784 g/m²/yr. The mean standing stock biomass was 0.14296 g/m², and the cohort production/biomass ratio was 3.902. The estimate of secondary production is important because it combines individual growth and population survivorship into a single measurement, which leads to a better understanding of the ecological importance of A. variegatus in the wood-dwelling aquatic insect community.