Mayflies are an important part of the diet for many species of fish. The adults are delicate, soft-bodied insects and range in size from approximately one quarter inch to over two inches long. When at rest, the wings are held together over the back. The immature stages develop in water for a period of a few weeks to a few years, depending on the species and water conditions. When the last aquatic stage leaves the water, it molts into a cloudy-winged stage called the subimago. The subimago soon molts into the true adult or imago stage. This stage has clear wings. Mayflies are the only insects that molt after they are able to fly.