Image showing the various stages in a cyclorrhapha flies life-cycle (middle and left). From the egg three larval stages follow. After some time feeding the third larval stage becomes a puparium, giving a hard protective case to the developing fly. The adult fly pushes off the top of its pupal case using a ballon like structure called a ptilinum. The right of the image shows the aquatic larval and pupal stages of a blackfly, Simulium.