Which mayfly family includes species that are typically found in fast-flowing water?

The Heptageniidae family of mayflies is known for its association with fast-flowing freshwater environments. Many species in this family have adapted to thrive in such habitats, displaying specific morphological and behavioral traits that enable them to maintain their position in moving water. For example, they often have flattened bodies and specialized gills that help them cling to substrates in rapid currents.

These adaptations allow Heptageniidae larvae to effectively feed on periphyton and detritus that accumulate in riffles and rocky substrates, making them an important part of the aquatic food web. This family includes genera like Epeorus and Rhithrogena, which are commonly found in streams and rivers with swift currents.

While other families of mayflies exist, they may have different habitat preferences or ecological roles that do not specifically cater to fast-flowing environments. For instance, Ephemeridae consists of species that can be found in a range of water types, including still waters, and the other families listed may not be as closely tied to fast currents as Heptageniidae.