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