Structure of insects

• Insects that have evolved to live on land have microscopic air-filled pipes called trachea

  • The tracheae divide into smaller tubes called tracheoles which continue to divide until they penetrate into individuals body cells
  • This means that gases are directly exchanged between cells and the atmosphere - there is no need to transport them
• Tracheae - A large internal network of tubes in insects with supported rings to prevent them collapsing
• Tracheoles - These tubes extend from the tracheae and extend throughout all the body tissues of the insect to allow atmospheric air to be brought directly to respiring tissues
• Spiracle - Tiny pores that allow gases to enter and leave the tracheae (and water vapour to leave as well). They are opened and closed by a valve
• Air enters the trachea through pores on the surface of the exoskeleton called spiracles. CO2 and O2 will diffuse in/out of the spiracles down their concentration gradient