Dukerschein, J. T., Wiener, J. G., Rada, R. G., and others, 1992, Cadmium and mercury in emergent mayflies (Hexagenia bilineata ) from the Upper Mississippi River.: Archives of Environmental Contamination and Toxicology, v. 23, no. 1, p. 109-116. Abstract Burrowing mayflies (Hexagenia bilineata ) were analyzed to assess longitudinal patterns in their cadmium and mercury content along the upper Mississippi River. Concentrations of mercury and cadmium in composite samples of female mayflies were not correlated, indicating dissimilar longitudinal patterns in concentrations of the two metals. Concentrations and burdens of both metals varied significantly between males and females; consequently, we recommend that programs involving analyses of mayflies to survey or monitor metals in aquatic systems analyze separately males and females. Keywords cadmium, mercury, bioaccumulation, Ephemeridae, Hexagenia-bilineata, Ephemeroptera, USA, Upper-Mississippi-R., heavy-metals, aquatic-insects, USA,-Mississippi-R.