Members of this family, commonly called micro-caddisflies are typically found in soft pouch-like cases made of minerals. As the common name suggests, they are tiny, but have rather bulbous abdomens. Like the Hydropsychidae, the dorsa of all three thoracic segments are sclerotized. Unlike them, however, they have no filamentous gills on their abdomens. The genus Hydroptila in particular is characterized by having three fleshy projections at the end of the abdomen.
Image of the three fleshy projections at the end of the abdomen.