There are 4 generas of Caenidae found in North America. Larvae and adults range from 2-8 mm in length and can be found in streams in areas with slow moving currents. They can also be found at the water's edge of lakes and wetlands. Caenidae are catergorized as collectors/gatherers and scrapers.
The operculate gills do not take up dissolved oxygen, but instead are used to cover and protect the other gills, which absorb dissolved oxygen from the water. Since these mayflies occur in areas where the current is slow, sediment can rapidly settle on the gills and prevent dissolved oxygen uptake. In order to keep the gills free of sediment, caenid mayflies wave their operculate gills.