Breathing tube on a fruit fly's pupa, coloured scanning electron micrograph (SEM). This structure is called a spiracle. This fruit fly is Drosophila melanogaster (wild type Oregon R), and its larva develop within a structure called a puparium, from which the pupal spiracles project outward. The anterior pair of spiracles terminate in tubelike extensions, called spiracular papillae. The exposed ends open in narrow slits, which take in air and pass it to the developing pupa. Magnification: x470 when printed 10 centimetres wide.