Unlike fish and mammals, insects do not have a circulatory system with blood that transports oxygen. Insects get the oxygen they need directly from the air. Insects have openings on the side of their bodies called spiracles. These spiracles have valves that the insect can actively open and close to allow more air to enter the body. Requirements for oxygen change depending on activity so when active, the valves are open, when not active, the valves close somewhat.
Tracheal tubes are tubes that connect the spiracle to the internal part of the body. As the tubes move into the body they branch continuously into smaller and smaller trachioles.