Mosquito pupa, coloured scanning electron micrograph (SEM). This is a pupa from a Culex mosquito. The pupa is less dense than water and floats at the surface. The developing mosquito inside the pupa takes oxygen through two breathing tubes at one end of the pupa (lower left). The metamorphosis of the mosquito into an adult is completed within this pupal case. Magnification: x18 when printed at 10 centimetres high.