Morphological and field observations of two coexisting microcaddisflies from a northeastern Ohio spring seepage and stream complex show both spatial and trophic resource partitioning. Ochrotrichia riesi inhabits the exposed bedrock substrate of the stream channel, as well as rocky seepages at the periphery of the stream, whereas Hydroptila consimilis is absent from the seepage areas. Ochrotrichia riesi is a strict scraper of periphyton, and H. consimilis attacks short filaments of the green alga Cladophora growing on the stream bottom. Mandible morphology differs for the two species, with O. riesi having robustly cusped mandibles suited for scraping rock substrate and H. consimilis having sharply pointed mandibles suited for piercing algal cells. These data, and the growing body of knowledge of the feeding habits and ecology of Hydroptilidae, support earlier hypotheses that subtle morphological and behavioral differences allow coexisting species to partition resources. Hydroptilidae is the world's largest family of Trichoptera, and resource partitioning of food and larval habitat may, in part, explain the high species richness.