A Mayfly is an invertebrate. Invertebrates are animals without backbones, such as caddisflies, worms and snails, that live for all or a portion of their lives in freshwater. The mayfly larvae lives under the water until its an adult mayfly. Once it is full grown, the mayfly flies to lay its eggs in another part of the river.
The scientific name for the mayfly is Deleatidium. It grows up to 2 cm long and has three long tails and well-developed legs. It breathes through gills that look like leaves on the sides of its body. Mayflies make quick, distinctive movements as they appear to undulate side-to-side.