Scanning electron micrograph of a spiracle, or breathing pore, on the thorax of the fruit fly, Drosophila melanogaster. The specimen is of the wild type of the fly, known as Oregon R. Thoracic spiracles are large & fringed with filter hairs. Air passes into the pores & is conveyed through the body by a network of tubes called tracheae. The diameter of the tubes becomes smaller, forming tracheoles. Oxygen is not carried in the blood of insects, but diffuses across the tracheal tubes directly into each cell. Tracheae are ingrowths of the body wall made of chitin. Spiracles occur in pairs on either side of most body segments. Magnification: x2000 at 8x10-inch size.