Photo by J. W. Stewart. Photo by Drees. Subimagoes have the wings cloudy in appearance while imagoes have clear wings. Some species may have the wings patterned. The thorax and the abdomen of mayflies are bare and often shiny.
Legs vary in size, with the front legs the longest and held forward when at rest.
Body color varies with species, including yellow, green, white and black. Adults and immatures are quite delicate. Aquatic immature stages are elongate, and flattened or cylindrical. They have short antennae. Their body color may be green or brown but may vary by the food that is eaten.