Studies of biodiversity and ecosystem function require to consider the identification level that accurately describes the functional diversity of communities, in terms of their biological traits, at different spatial scales. Therefore, we combined three published data sets of stream macroinvertebrate abundances collected at three spatial scales with a database of functional species traits (e.g. life history, morphology, physiology, and behaviour). We investigated the abundance of taxa and their traits at five levels of taxonomic (from species to class) and three levels of spatial resolution (from local habitat to catchment). We used multivariate analyses and correlations to evaluate the accuracy of community descriptions through the stability of such descriptions, the degree of similarity of site ordinations, and the overall community structure expressed at each taxonomic level. The accuracy of community descriptions based on the abundance of taxa depended on the spatial scale considered. The accurate description of the abundance of taxa required identifications to genera and/or families on the local habitat scale, while species identifications were needed on the catchment scale. In contrast, the accurate description of the abundance of biological traits was achieved by identifications to species, genera, or families on all three spatial scales. Thus, species identifications may not be necessary for future studies on the functional diversity of the stream benthos at different spatial scales.