We determined the life history, secondary production, and trophic basis of production for Callibaetis fluctuans in a mitigated wetland at the Green Bottom Wildlife Management Area, Cabell County, West Virginia, USA. Quantitative benthic samples were collected from three sites covering a range of water depths and vegetation types from January to December 1994. Length-frequency histograms were constructed for each sample date, and secondary production was calculated using the size-frequency method. Foregut analyses were conducted seasonally to determine diet. Callibaetis fluctuans had a multivoltine life cycle with at least three cohorts. Fast larval growth occurred during the spring and fall, whereas an overwintering cohort had slower growth. Total annual production was 208.0 mg·m⁻²·yr⁻¹ (AFDM) with a production-to-biomass ratio of 12.6. Amorphous detritus comprised >80% of the diet in all seasons and accounted for 70% of total production. To account for this production, C. fluctuans consumed 3675 mg·m⁻²·yr⁻¹ of detritus. This is one of the first studies to provide production estimates for an aquatic insect in a permanently inundated wetland.