In the winged stages mayflies are very susceptible to predation, especially by birds and this stage has evolved to be extremely short-lived in comparison to the aquatic nymphal stage. Adult mayflies are fragile insects, and can be distinguished from other insects by a long narrow body ending in two or three long tail filaments which are usually longer than the body. The nymphs, which appear quite different from the adults, have chewing mouthparts, and several pairs of lateral gills along the abdomen for extracting oxygen from the water. The abdomen terminates in three or sometimes two moderately long cerci. In more mature nymphs, developing wing pads are quite evident on the top of the thorax.
Mayflies serve as food for many fishes and predaceous insects, such as dragonflies.
They, along with other aquatic insects, serve an important function in streams, shredding and breaking down leaves and other litter that otherwise would accumulate and eventually clog Sri Lanka's streams. Nitrates and phosphates are also removed from streams by being incorporated into the bodies of these insects. In many parts of the world, particularly temperate areas, the emergence of adult mayflies is very seasonal, most species emerging in a short synchronous period. However, in Sri Lanka, I have found no evidence of periodicity, and it appears that most Sri Lankan mayflies emerge throughout the year in an aseasonal pattern. Mayflies are an ancient group of insects, with fossils known from over 200 million years ago.