A comparison of the taxonomic composition, relative abundance, diet, feeding habitat, and size of live and dead insects was conducted in Willcox Playa, an ephemeral lake in southeastern Arizona. Death assemblages of beetles, the most abundant group of insects in this study, are preserved in the shallow, subsurface sediments along the shoreline of the lake. Fifty-six percent of the living beetle families and twenty-eight percent of the living beetle genera were found in the sediments; one-hundred percent of the families and ninety-one percent of the genera found dead were also present in the live fauna. Relative abundances of beetle families in the live assemblage are significantly different than relative abundances in the death assemblage. Among diet and habitat groups, necrophagous and ground-dwelling beetles are over-represented in the death assemblage, while wood-inhabitants and aquatics are under-represented. The death assemblage contains a greater proportion of smaller, more robust beetles. Such biases also may occur in fossil assemblages and should be considered in paleoecological and paleoenvironmental reconstructions.